* [syzbot] [mptcp?] general protection fault in proc_scheduler
@ 2025-01-02 14:12 syzbot
2025-01-02 15:21 ` Eric Dumazet
0 siblings, 1 reply; 22+ messages in thread
From: syzbot @ 2025-01-02 14:12 UTC (permalink / raw)
To: davem, edumazet, geliang, horms, kuba, linux-kernel, martineau,
matttbe, mptcp, netdev, pabeni, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
__kernel_write_iter+0x318/0xa80 fs/read_write.c:612
__kernel_write+0xf6/0x140 fs/read_write.c:632
do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
acct_pin_kill+0x2d/0x100 kernel/acct.c:192
pin_kill+0x194/0x7c0 fs/fs_pin.c:44
mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
task_work_run+0x14e/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0xad8/0x2d70 kernel/exit.c:938
do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
get_signal+0x2576/0x2610 kernel/signal.c:3017
arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fee3cb87a6a
Code: Unable to access opcode bytes at 0x7fee3cb87a40.
RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 1 bytes skipped:
0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
5: 0f 85 fe 02 00 00 jne 0x309
b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
12: 00
13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
1a: fc ff df
1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
22: 48 89 fa mov %rdi,%rdx
25: 48 c1 ea 03 shr $0x3,%rdx
* 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
2d: 0f 85 cc 02 00 00 jne 0x2ff
33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
38: 48 rex.W
39: 8d .byte 0x8d
3a: 84 24 c8 test %ah,(%rax,%rcx,8)
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-02 14:12 [syzbot] [mptcp?] general protection fault in proc_scheduler syzbot
@ 2025-01-02 15:21 ` Eric Dumazet
2025-01-04 18:38 ` Matthieu Baerts
0 siblings, 1 reply; 22+ messages in thread
From: Eric Dumazet @ 2025-01-02 15:21 UTC (permalink / raw)
To: syzbot, Al Viro
Cc: davem, geliang, horms, kuba, linux-kernel, martineau, matttbe,
mptcp, netdev, pabeni, syzkaller-bugs
On Thu, Jan 2, 2025 at 3:12 PM syzbot
<syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
>
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>
> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
> __kernel_write+0xf6/0x140 fs/read_write.c:632
> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
> task_work_run+0x14e/0x250 kernel/task_work.c:239
> exit_task_work include/linux/task_work.h:43 [inline]
> do_exit+0xad8/0x2d70 kernel/exit.c:938
> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
> get_signal+0x2576/0x2610 kernel/signal.c:3017
> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fee3cb87a6a
> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess), 1 bytes skipped:
> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
> 5: 0f 85 fe 02 00 00 jne 0x309
> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
> 12: 00
> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> 1a: fc ff df
> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
> 22: 48 89 fa mov %rdi,%rdx
> 25: 48 c1 ea 03 shr $0x3,%rdx
> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> 2d: 0f 85 cc 02 00 00 jne 0x2ff
> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
> 38: 48 rex.W
> 39: 8d .byte 0x8d
> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
I thought acct(2) was only allowing regular files.
acct_on() indeed has :
if (!S_ISREG(file_inode(file)->i_mode)) {
kfree(acct);
filp_close(file, NULL);
return -EACCES;
}
It seems there are other ways to call do_acct_process() targeting a sysfs file ?
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-02 15:21 ` Eric Dumazet
@ 2025-01-04 18:38 ` Matthieu Baerts
2025-01-04 18:53 ` Eric Dumazet
0 siblings, 1 reply; 22+ messages in thread
From: Matthieu Baerts @ 2025-01-04 18:38 UTC (permalink / raw)
To: Eric Dumazet
Cc: davem, geliang, horms, kuba, linux-kernel, martineau, mptcp,
netdev, pabeni, syzkaller-bugs, syzbot, Al Viro
Hi Eric,
Thank you for the bug report!
On 02/01/2025 16:21, Eric Dumazet wrote:
> On Thu, Jan 2, 2025 at 3:12 PM syzbot
> <syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
>> git tree: upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
>> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
>>
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
>>
>> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
>> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>>
>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>> <TASK>
>> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
>> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
>> __kernel_write+0xf6/0x140 fs/read_write.c:632
>> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
>> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
>> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
>> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
>> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
>> task_work_run+0x14e/0x250 kernel/task_work.c:239
>> exit_task_work include/linux/task_work.h:43 [inline]
>> do_exit+0xad8/0x2d70 kernel/exit.c:938
>> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
>> get_signal+0x2576/0x2610 kernel/signal.c:3017
>> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
>> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
>> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
>> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
>> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
>> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> RIP: 0033:0x7fee3cb87a6a
>> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
>> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
>> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
>> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
>> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
>> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
>> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
>> </TASK>
>> Modules linked in:
>> ---[ end trace 0000000000000000 ]---
>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> ----------------
>> Code disassembly (best guess), 1 bytes skipped:
>> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
>> 5: 0f 85 fe 02 00 00 jne 0x309
>> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
>> 12: 00
>> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
>> 1a: fc ff df
>> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
>> 22: 48 89 fa mov %rdi,%rdx
>> 25: 48 c1 ea 03 shr $0x3,%rdx
>> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
>> 2d: 0f 85 cc 02 00 00 jne 0x2ff
>> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
>> 38: 48 rex.W
>> 39: 8d .byte 0x8d
>> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
(...)
> I thought acct(2) was only allowing regular files.
>
> acct_on() indeed has :
>
> if (!S_ISREG(file_inode(file)->i_mode)) {
> kfree(acct);
> filp_close(file, NULL);
> return -EACCES;
> }
>
> It seems there are other ways to call do_acct_process() targeting a sysfs file ?
Just to be sure I'm not misunderstanding your comment: do you mean that
here, the issue is *not* in MPTCP code where we get the 'struct net'
pointer via 'current->nsproxy->net_ns', but in the FS part, right?
Here, we have an issue because 'current->nsproxy' is NULL, but is it
normal? Or should we simply exit with an error if it is the case because
we are in an exiting phase?
I'm just a bit confused, because it looks like 'net' is retrieved from
different places elsewhere when dealing with sysfs: some get it from
'current' like us, some assign 'net' to 'table->extra2', others get it
from 'table->data' (via a container_of()), etc. Maybe we should not use
'current->nsproxy->net_ns' here then?
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 18:38 ` Matthieu Baerts
@ 2025-01-04 18:53 ` Eric Dumazet
2025-01-04 19:00 ` Al Viro
` (2 more replies)
0 siblings, 3 replies; 22+ messages in thread
From: Eric Dumazet @ 2025-01-04 18:53 UTC (permalink / raw)
To: Matthieu Baerts
Cc: davem, geliang, horms, kuba, linux-kernel, martineau, mptcp,
netdev, pabeni, syzkaller-bugs, syzbot, Al Viro
On Sat, Jan 4, 2025 at 7:38 PM Matthieu Baerts <matttbe@kernel.org> wrote:
>
> Hi Eric,
>
> Thank you for the bug report!
>
> On 02/01/2025 16:21, Eric Dumazet wrote:
> > On Thu, Jan 2, 2025 at 3:12 PM syzbot
> > <syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
> >>
> >> Hello,
> >>
> >> syzbot found the following issue on:
> >>
> >> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
> >> git tree: upstream
> >> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
> >> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
> >> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
> >> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
> >>
> >> Downloadable assets:
> >> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
> >> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
> >> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
> >>
> >> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> >> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
> >>
> >> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
> >> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
> >> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
> >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> >> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> >> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> >> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> >>
> >> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> >> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> >> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> >> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> >> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> >> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >> Call Trace:
> >> <TASK>
> >> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
> >> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
> >> __kernel_write+0xf6/0x140 fs/read_write.c:632
> >> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
> >> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
> >> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
> >> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
> >> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
> >> task_work_run+0x14e/0x250 kernel/task_work.c:239
> >> exit_task_work include/linux/task_work.h:43 [inline]
> >> do_exit+0xad8/0x2d70 kernel/exit.c:938
> >> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
> >> get_signal+0x2576/0x2610 kernel/signal.c:3017
> >> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
> >> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
> >> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
> >> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
> >> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
> >> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
> >> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >> RIP: 0033:0x7fee3cb87a6a
> >> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
> >> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
> >> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
> >> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
> >> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
> >> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
> >> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
> >> </TASK>
> >> Modules linked in:
> >> ---[ end trace 0000000000000000 ]---
> >> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> >> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> >> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> >> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> >> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> >> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> >> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> >> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> >> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >> ----------------
> >> Code disassembly (best guess), 1 bytes skipped:
> >> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
> >> 5: 0f 85 fe 02 00 00 jne 0x309
> >> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
> >> 12: 00
> >> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> >> 1a: fc ff df
> >> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
> >> 22: 48 89 fa mov %rdi,%rdx
> >> 25: 48 c1 ea 03 shr $0x3,%rdx
> >> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> >> 2d: 0f 85 cc 02 00 00 jne 0x2ff
> >> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
> >> 38: 48 rex.W
> >> 39: 8d .byte 0x8d
> >> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
>
> (...)
>
> > I thought acct(2) was only allowing regular files.
> >
> > acct_on() indeed has :
> >
> > if (!S_ISREG(file_inode(file)->i_mode)) {
> > kfree(acct);
> > filp_close(file, NULL);
> > return -EACCES;
> > }
> >
> > It seems there are other ways to call do_acct_process() targeting a sysfs file ?
>
> Just to be sure I'm not misunderstanding your comment: do you mean that
> here, the issue is *not* in MPTCP code where we get the 'struct net'
> pointer via 'current->nsproxy->net_ns', but in the FS part, right?
>
> Here, we have an issue because 'current->nsproxy' is NULL, but is it
> normal? Or should we simply exit with an error if it is the case because
> we are in an exiting phase?
>
> I'm just a bit confused, because it looks like 'net' is retrieved from
> different places elsewhere when dealing with sysfs: some get it from
> 'current' like us, some assign 'net' to 'table->extra2', others get it
> from 'table->data' (via a container_of()), etc. Maybe we should not use
> 'current->nsproxy->net_ns' here then?
I do think this is a bug in process accounting, not in networking.
It might make sense to output a record on a regular file, but probably
not on any other files.
diff --git a/kernel/acct.c b/kernel/acct.c
index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
const struct cred *orig_cred;
struct file *file = acct->file;
+ if (S_ISREG(file_inode(file)->i_mode))
+ return;
+
/*
* Accounting records are not subject to resource limits.
*/
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 18:53 ` Eric Dumazet
@ 2025-01-04 19:00 ` Al Viro
2025-01-04 19:11 ` Matthieu Baerts
2025-01-04 19:11 ` Matthieu Baerts
2025-01-04 20:09 ` Al Viro
2 siblings, 1 reply; 22+ messages in thread
From: Al Viro @ 2025-01-04 19:00 UTC (permalink / raw)
To: Eric Dumazet
Cc: Matthieu Baerts, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sat, Jan 04, 2025 at 07:53:22PM +0100, Eric Dumazet wrote:
> I do think this is a bug in process accounting, not in networking.
>
> It might make sense to output a record on a regular file, but probably
> not on any other files.
>
> diff --git a/kernel/acct.c b/kernel/acct.c
> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
> 100644
> --- a/kernel/acct.c
> +++ b/kernel/acct.c
> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
> const struct cred *orig_cred;
> struct file *file = acct->file;
>
> + if (S_ISREG(file_inode(file)->i_mode))
> + return;
... won't help, since the file in question *is* a regular file. IOW, it's
a wrong predicate here.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 19:00 ` Al Viro
@ 2025-01-04 19:11 ` Matthieu Baerts
2025-01-04 20:21 ` Al Viro
0 siblings, 1 reply; 22+ messages in thread
From: Matthieu Baerts @ 2025-01-04 19:11 UTC (permalink / raw)
To: Al Viro, Eric Dumazet
Cc: davem, geliang, horms, kuba, linux-kernel, martineau, mptcp,
netdev, pabeni, syzkaller-bugs, syzbot
Hi Al, Eric,
On 04/01/2025 20:00, Al Viro wrote:
> On Sat, Jan 04, 2025 at 07:53:22PM +0100, Eric Dumazet wrote:
>
>> I do think this is a bug in process accounting, not in networking.
>>
>> It might make sense to output a record on a regular file, but probably
>> not on any other files.
>>
>> diff --git a/kernel/acct.c b/kernel/acct.c
>> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
>> 100644
>> --- a/kernel/acct.c
>> +++ b/kernel/acct.c
>> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
>> const struct cred *orig_cred;
>> struct file *file = acct->file;
>>
>> + if (S_ISREG(file_inode(file)->i_mode))
>> + return;
>
> ... won't help, since the file in question *is* a regular file. IOW, it's
> a wrong predicate here.
On my side, it looks like I'm not able to reproduce the issue with this
patch. Without it, it is very easy to reproduce it. (But I don't know if
there are other consequences that would avoid the issue to happen: when
looking at the logs, with the patch, I don't have heaps of "Process
accounting resumed" messages that I had before.)
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 18:53 ` Eric Dumazet
2025-01-04 19:00 ` Al Viro
@ 2025-01-04 19:11 ` Matthieu Baerts
2025-01-06 13:32 ` Joel Granados
2025-01-04 20:09 ` Al Viro
2 siblings, 1 reply; 22+ messages in thread
From: Matthieu Baerts @ 2025-01-04 19:11 UTC (permalink / raw)
To: Eric Dumazet
Cc: davem, geliang, horms, kuba, linux-kernel, martineau, mptcp,
netdev, pabeni, syzkaller-bugs, syzbot, Al Viro, Joel Granados
Hi Eric,
(+cc Joel)
Thank you for your reply!
On 04/01/2025 19:53, Eric Dumazet wrote:
> On Sat, Jan 4, 2025 at 7:38 PM Matthieu Baerts <matttbe@kernel.org> wrote:
>>
>> Hi Eric,
>>
>> Thank you for the bug report!
>>
>> On 02/01/2025 16:21, Eric Dumazet wrote:
>>> On Thu, Jan 2, 2025 at 3:12 PM syzbot
>>> <syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>> syzbot found the following issue on:
>>>>
>>>> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
>>>> git tree: upstream
>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
>>>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
>>>>
>>>> Downloadable assets:
>>>> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
>>>> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
>>>> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
>>>>
>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>>> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
>>>>
>>>> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
>>>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
>>>> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>>>>
>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>> Call Trace:
>>>> <TASK>
>>>> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
>>>> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
>>>> __kernel_write+0xf6/0x140 fs/read_write.c:632
>>>> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
>>>> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
>>>> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
>>>> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
>>>> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
>>>> task_work_run+0x14e/0x250 kernel/task_work.c:239
>>>> exit_task_work include/linux/task_work.h:43 [inline]
>>>> do_exit+0xad8/0x2d70 kernel/exit.c:938
>>>> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
>>>> get_signal+0x2576/0x2610 kernel/signal.c:3017
>>>> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
>>>> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
>>>> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
>>>> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
>>>> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
>>>> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
>>>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>>> RIP: 0033:0x7fee3cb87a6a
>>>> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
>>>> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
>>>> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
>>>> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
>>>> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
>>>> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
>>>> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
>>>> </TASK>
>>>> Modules linked in:
>>>> ---[ end trace 0000000000000000 ]---
>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>> ----------------
>>>> Code disassembly (best guess), 1 bytes skipped:
>>>> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
>>>> 5: 0f 85 fe 02 00 00 jne 0x309
>>>> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
>>>> 12: 00
>>>> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
>>>> 1a: fc ff df
>>>> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
>>>> 22: 48 89 fa mov %rdi,%rdx
>>>> 25: 48 c1 ea 03 shr $0x3,%rdx
>>>> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
>>>> 2d: 0f 85 cc 02 00 00 jne 0x2ff
>>>> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
>>>> 38: 48 rex.W
>>>> 39: 8d .byte 0x8d
>>>> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
>>
>> (...)
>>
>>> I thought acct(2) was only allowing regular files.
>>>
>>> acct_on() indeed has :
>>>
>>> if (!S_ISREG(file_inode(file)->i_mode)) {
>>> kfree(acct);
>>> filp_close(file, NULL);
>>> return -EACCES;
>>> }
>>>
>>> It seems there are other ways to call do_acct_process() targeting a sysfs file ?
>>
>> Just to be sure I'm not misunderstanding your comment: do you mean that
>> here, the issue is *not* in MPTCP code where we get the 'struct net'
>> pointer via 'current->nsproxy->net_ns', but in the FS part, right?
>>
>> Here, we have an issue because 'current->nsproxy' is NULL, but is it
>> normal? Or should we simply exit with an error if it is the case because
>> we are in an exiting phase?
>>
>> I'm just a bit confused, because it looks like 'net' is retrieved from
>> different places elsewhere when dealing with sysfs: some get it from
>> 'current' like us, some assign 'net' to 'table->extra2', others get it
>> from 'table->data' (via a container_of()), etc. Maybe we should not use
>> 'current->nsproxy->net_ns' here then?
>
> I do think this is a bug in process accounting, not in networking.
>
> It might make sense to output a record on a regular file, but probably
> not on any other files.
>
> diff --git a/kernel/acct.c b/kernel/acct.c
> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
> 100644
> --- a/kernel/acct.c
> +++ b/kernel/acct.c
> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
> const struct cred *orig_cred;
> struct file *file = acct->file;
>
> + if (S_ISREG(file_inode(file)->i_mode))
> + return;
> +
> /*
> * Accounting records are not subject to resource limits.
> */
OK, thank you, that's clearer.
So this is then more a question for Joel, right?
Do you plan to send this patch to him?
#syz set subsystems: fs
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 18:53 ` Eric Dumazet
2025-01-04 19:00 ` Al Viro
2025-01-04 19:11 ` Matthieu Baerts
@ 2025-01-04 20:09 ` Al Viro
2 siblings, 0 replies; 22+ messages in thread
From: Al Viro @ 2025-01-04 20:09 UTC (permalink / raw)
To: Eric Dumazet
Cc: Matthieu Baerts, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sat, Jan 04, 2025 at 07:53:22PM +0100, Eric Dumazet wrote:
> I do think this is a bug in process accounting, not in networking.
>
> It might make sense to output a record on a regular file, but probably
> not on any other files.
>
> diff --git a/kernel/acct.c b/kernel/acct.c
> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
> 100644
> --- a/kernel/acct.c
> +++ b/kernel/acct.c
> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
> const struct cred *orig_cred;
> struct file *file = acct->file;
>
> + if (S_ISREG(file_inode(file)->i_mode))
> + return;
Wait, what? OK, that will stop attempts to write there - or to any
other regular file.
If you modify that to
if (!S_ISREG(...))
you seem to have intended, it won't break the normal behaviour but it
won't help with sysctls.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 19:11 ` Matthieu Baerts
@ 2025-01-04 20:21 ` Al Viro
2025-01-05 8:32 ` Eric Dumazet
2025-01-05 17:03 ` Matthieu Baerts
0 siblings, 2 replies; 22+ messages in thread
From: Al Viro @ 2025-01-04 20:21 UTC (permalink / raw)
To: Matthieu Baerts
Cc: Eric Dumazet, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sat, Jan 04, 2025 at 08:11:49PM +0100, Matthieu Baerts wrote:
> >> + if (S_ISREG(file_inode(file)->i_mode))
^^^^^^^^^
> >> + return;
> >
> > ... won't help, since the file in question *is* a regular file. IOW, it's
> > a wrong predicate here.
>
> On my side, it looks like I'm not able to reproduce the issue with this
> patch. Without it, it is very easy to reproduce it. (But I don't know if
> there are other consequences that would avoid the issue to happen: when
> looking at the logs, with the patch, I don't have heaps of "Process
> accounting resumed" messages that I had before.)
Unsurprisingly so, since it rejects all regular files due to a typo;
fix that and you'll see that the oops is still there.
The real issue (and the one that affects more than just this scenario) is
the use of current->nsproxy->net to get to the damn thing.
Why not something like
static int proc_scheduler(const struct ctl_table *ctl, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
char (*data)[MPTCP_SCHED_NAME_MAX] = table->data;
char val[MPTCP_SCHED_NAME_MAX];
struct ctl_table tbl = {
.data = val,
.maxlen = MPTCP_SCHED_NAME_MAX,
};
int ret;
strscpy(val, *data, MPTCP_SCHED_NAME_MAX);
ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
if (write && ret == 0) {
rcu_read_lock();
sched = mptcp_sched_find(val);
if (sched)
strscpy(*data, val, MPTCP_SCHED_NAME_MAX);
else
ret = -ENOENT;
rcu_read_unlock();
}
return ret;
}
seeing that the data object you really want to access is
mptcp_get_pernet(net)->scheduler and you have that pointer
stored in table->data at the registration time?
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 20:21 ` Al Viro
@ 2025-01-05 8:32 ` Eric Dumazet
2025-01-05 11:29 ` Al Viro
2025-01-05 17:03 ` Matthieu Baerts
1 sibling, 1 reply; 22+ messages in thread
From: Eric Dumazet @ 2025-01-05 8:32 UTC (permalink / raw)
To: Al Viro
Cc: Matthieu Baerts, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sat, Jan 4, 2025 at 9:21 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Sat, Jan 04, 2025 at 08:11:49PM +0100, Matthieu Baerts wrote:
> > >> + if (S_ISREG(file_inode(file)->i_mode))
> ^^^^^^^^^
> > >> + return;
> > >
> > > ... won't help, since the file in question *is* a regular file. IOW, it's
> > > a wrong predicate here.
> >
> > On my side, it looks like I'm not able to reproduce the issue with this
> > patch. Without it, it is very easy to reproduce it. (But I don't know if
> > there are other consequences that would avoid the issue to happen: when
> > looking at the logs, with the patch, I don't have heaps of "Process
> > accounting resumed" messages that I had before.)
>
> Unsurprisingly so, since it rejects all regular files due to a typo;
> fix that and you'll see that the oops is still there.
>
> The real issue (and the one that affects more than just this scenario) is
> the use of current->nsproxy->net to get to the damn thing.
According to grep, we have many other places directly reading
current->nsproxy->net_ns
For instance in net/sctp/sysctl.c
Should we change them all ?
Perhaps an alternative would be to add a generic check in
proc_sys_call_handler()
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 27a283d85a6e7df1a7edbfb513ce75832363e2e6..84968b10ce86e7fd88c6e3c43f52b601394b056f
100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -576,6 +576,8 @@ static ssize_t proc_sys_call_handler(struct kiocb
*iocb, struct iov_iter *iter,
error = -EINVAL;
if (!table->proc_handler)
goto out;
+ if (unlikely(current->flags & PF_EXITING))
+ goto out;
/* don't even try if the size is too large */
error = -ENOMEM;
Thanks.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-05 8:32 ` Eric Dumazet
@ 2025-01-05 11:29 ` Al Viro
2025-01-05 16:52 ` Eric Dumazet
0 siblings, 1 reply; 22+ messages in thread
From: Al Viro @ 2025-01-05 11:29 UTC (permalink / raw)
To: Eric Dumazet
Cc: Matthieu Baerts, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sun, Jan 05, 2025 at 09:32:36AM +0100, Eric Dumazet wrote:
> According to grep, we have many other places directly reading
> current->nsproxy->net_ns
> For instance in net/sctp/sysctl.c
> Should we change them all ?
Depends - do you want their contents match the netns of opener (as,
AFAICS, for ipv4 sysctls) or that of the reader?
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-05 11:29 ` Al Viro
@ 2025-01-05 16:52 ` Eric Dumazet
2025-01-05 17:03 ` Matthieu Baerts
2025-01-05 19:54 ` Al Viro
0 siblings, 2 replies; 22+ messages in thread
From: Eric Dumazet @ 2025-01-05 16:52 UTC (permalink / raw)
To: Al Viro
Cc: Matthieu Baerts, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sun, Jan 5, 2025 at 12:29 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Sun, Jan 05, 2025 at 09:32:36AM +0100, Eric Dumazet wrote:
>
> > According to grep, we have many other places directly reading
> > current->nsproxy->net_ns
> > For instance in net/sctp/sysctl.c
> > Should we change them all ?
>
> Depends - do you want their contents match the netns of opener (as,
> AFAICS, for ipv4 sysctls) or that of the reader?
I am only worried that a malicious user could crash the host with
current kernels,
not about this MPTP crash, but all unaware users of current->nsproxy
in sysctl handlers.
Back to MPTCP :
Using the convention used in other mptcp sysctls like (enabled,
add_addr_timeout,
checksum_enabled, allow_join_initial_addr_port...) is better for consistency.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-05 16:52 ` Eric Dumazet
@ 2025-01-05 17:03 ` Matthieu Baerts
2025-01-05 19:54 ` Al Viro
1 sibling, 0 replies; 22+ messages in thread
From: Matthieu Baerts @ 2025-01-05 17:03 UTC (permalink / raw)
To: Eric Dumazet, Al Viro
Cc: davem, geliang, horms, kuba, linux-kernel, martineau, mptcp,
netdev, pabeni, syzkaller-bugs, syzbot
Hi Eric,
On 05/01/2025 17:52, Eric Dumazet wrote:
> On Sun, Jan 5, 2025 at 12:29 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>>
>> On Sun, Jan 05, 2025 at 09:32:36AM +0100, Eric Dumazet wrote:
>>
>>> According to grep, we have many other places directly reading
>>> current->nsproxy->net_ns
>>> For instance in net/sctp/sysctl.c
>>> Should we change them all ?
>>
>> Depends - do you want their contents match the netns of opener (as,
>> AFAICS, for ipv4 sysctls) or that of the reader?
>
> I am only worried that a malicious user could crash the host with
> current kernels,
> not about this MPTP crash, but all unaware users of current->nsproxy
> in sysctl handlers.
>
> Back to MPTCP :
>
> Using the convention used in other mptcp sysctls like (enabled,
> add_addr_timeout,
> checksum_enabled, allow_join_initial_addr_port...) is better for consistency.
Indeed, I can do the modifications to stop using current->nsproxy in
MPTCP. I can do the same in SCTP.
Do you plan to send your patch modifying proc_sysctl.c? It is just to
know if I should mark my patches as fixes, and split them to ease the
backports -- each helper using current->nsproxy has been introduced in
different commits -- or if I can send them to net-next instead.
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 20:21 ` Al Viro
2025-01-05 8:32 ` Eric Dumazet
@ 2025-01-05 17:03 ` Matthieu Baerts
1 sibling, 0 replies; 22+ messages in thread
From: Matthieu Baerts @ 2025-01-05 17:03 UTC (permalink / raw)
To: Al Viro
Cc: Eric Dumazet, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
Hi Al,
On 04/01/2025 21:21, Al Viro wrote:
> The real issue (and the one that affects more than just this scenario) is
> the use of current->nsproxy->net to get to the damn thing.
>
> Why not something like
(...)
> seeing that the data object you really want to access is
> mptcp_get_pernet(net)->scheduler and you have that pointer
> stored in table->data at the registration time?
Good point, thank you for the suggestion! :)
I will do this modification.
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-05 16:52 ` Eric Dumazet
2025-01-05 17:03 ` Matthieu Baerts
@ 2025-01-05 19:54 ` Al Viro
2025-01-05 20:50 ` Al Viro
1 sibling, 1 reply; 22+ messages in thread
From: Al Viro @ 2025-01-05 19:54 UTC (permalink / raw)
To: Eric Dumazet
Cc: Matthieu Baerts, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sun, Jan 05, 2025 at 05:52:19PM +0100, Eric Dumazet wrote:
> On Sun, Jan 5, 2025 at 12:29 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > On Sun, Jan 05, 2025 at 09:32:36AM +0100, Eric Dumazet wrote:
> >
> > > According to grep, we have many other places directly reading
> > > current->nsproxy->net_ns
> > > For instance in net/sctp/sysctl.c
> > > Should we change them all ?
> >
> > Depends - do you want their contents match the netns of opener (as,
> > AFAICS, for ipv4 sysctls) or that of the reader?
>
> I am only worried that a malicious user could crash the host with
> current kernels,
> not about this MPTP crash, but all unaware users of current->nsproxy
> in sysctl handlers.
I don't hate your mitigation in proc_sysctl.c, but IMO there are two
problems mixed here - one is that we probably should have access
to per-netns sysctl table act on the netns it had been created for,
which may not coincide with reader's/writer's netns and another is that
access to current->nsproxy->netns would simply oops if attempted when
current->nsproxy had been dropped.
So I suspect that current->nsproxy->netns shouldn't be used in
per-netns sysctls for consistency sake (note that it can get more
serious than just consistency, if you have e.g. a spinlock taken
in something hanging off current netns to protect access to
something table->data points to).
As for the mitigation in fs/proc/proc_sysctl.c... might be useful,
if it comes with a clear comment about the reasons it's there.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-05 19:54 ` Al Viro
@ 2025-01-05 20:50 ` Al Viro
2025-01-05 21:11 ` Al Viro
0 siblings, 1 reply; 22+ messages in thread
From: Al Viro @ 2025-01-05 20:50 UTC (permalink / raw)
To: Eric Dumazet
Cc: Matthieu Baerts, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sun, Jan 05, 2025 at 07:54:34PM +0000, Al Viro wrote:
> So I suspect that current->nsproxy->netns shouldn't be used in
> per-netns sysctls for consistency sake (note that it can get more
> serious than just consistency, if you have e.g. a spinlock taken
> in something hanging off current netns to protect access to
> something table->data points to).
>
> As for the mitigation in fs/proc/proc_sysctl.c... might be useful,
> if it comes with a clear comment about the reasons it's there.
FWIW, looks like we have two such in mptcp (with sysctls next to
those definitely accessing the netns of opener rather than reader/writer),
two in rds (both inconsistent on the write side -
struct net *net = current->nsproxy->net_ns;
int err;
err = proc_dointvec_minmax(ctl, write, buffer, lenp, fpos);
if (err < 0) {
pr_warn("Invalid input. Must be >= %d\n",
*(int *)(ctl->extra1));
return err;
}
if (write)
rds_tcp_sysctl_reset(net);
will modify ctl->data, which points to &rtn->{snd,rcv}buf_size, with
rtn == net_generic(net, rds_tcp_netid) and net being for opener's netns
and then call rds_tcp_sysctl_reset(net) with net being the writer's
netns) and 6 in sctp. At least some of sctp ones are also inconsistent
on the write side; e.g.
static int proc_sctp_do_rto_min(const struct ctl_table *ctl, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
struct net *net = current->nsproxy->net_ns;
unsigned int min = *(unsigned int *) ctl->extra1;
unsigned int max = *(unsigned int *) ctl->extra2;
struct ctl_table tbl;
int ret, new_value;
memset(&tbl, 0, sizeof(struct ctl_table));
tbl.maxlen = sizeof(unsigned int);
if (write)
tbl.data = &new_value;
else
tbl.data = &net->sctp.rto_min;
ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
if (write && ret == 0) {
if (new_value > max || new_value < min)
return -EINVAL;
net->sctp.rto_min = new_value;
}
return ret;
}
has max taken from ctl->extra2, which is &net->sctp.rto_max of the
opener's netns, but the value capped by that in stored into
net->sctp.rto_min of *writer's* netns. So the logics that is supposed
to prevent rto_min > rto_max can be bypassed; no idea how much can that
escalate to, but it's clearly not what the code intends.
So I'd rather document the "don't assume that current->nsproxy->netns will
point to the same netns this ctl is for" and fix those 10 instances - at
least some smell seriously fishy. It's not just the acct(2) weirdness and
the damage may be worse than an oops...
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-05 20:50 ` Al Viro
@ 2025-01-05 21:11 ` Al Viro
0 siblings, 0 replies; 22+ messages in thread
From: Al Viro @ 2025-01-05 21:11 UTC (permalink / raw)
To: Eric Dumazet
Cc: Matthieu Baerts, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Sun, Jan 05, 2025 at 08:50:56PM +0000, Al Viro wrote:
> has max taken from ctl->extra2, which is &net->sctp.rto_max of the
> opener's netns, but the value capped by that in stored into
> net->sctp.rto_min of *writer's* netns. So the logics that is supposed
> to prevent rto_min > rto_max can be bypassed; no idea how much can that
> escalate to, but it's clearly not what the code intends.
Speaking of which, the logics that tries to maintain rto_min <= rto_max is
broken in another way. There's no exclusion in those suckers. IOW, if
we have set rto_min to 1 and rto_max to 10000, two processes can try to
write 1000 to rto_min and 10 to rto_max resp., with successful validations
done against the original state in both, followed by actual stores.
Result is rto_min == 1000 and rto_max == 10, which is probably not what
one wants there...
IOW, the validation and stores should be atomic; the same goes for another
pair (pf_retrans <= ps_retrans). Again, I've no idea how severe it is,
but result seems to be at least contrary to expectation of the code
authors...
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-04 19:11 ` Matthieu Baerts
@ 2025-01-06 13:32 ` Joel Granados
2025-01-06 14:27 ` Matthieu Baerts
0 siblings, 1 reply; 22+ messages in thread
From: Joel Granados @ 2025-01-06 13:32 UTC (permalink / raw)
To: Matthieu Baerts
Cc: Eric Dumazet, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot, Al Viro
On Sat, Jan 04, 2025 at 08:11:52PM +0100, Matthieu Baerts wrote:
> Hi Eric,
>
> (+cc Joel)
>
> Thank you for your reply!
>
> On 04/01/2025 19:53, Eric Dumazet wrote:
> > On Sat, Jan 4, 2025 at 7:38 PM Matthieu Baerts <matttbe@kernel.org> wrote:
> >>
> >> Hi Eric,
> >>
> >> Thank you for the bug report!
> >>
> >> On 02/01/2025 16:21, Eric Dumazet wrote:
> >>> On Thu, Jan 2, 2025 at 3:12 PM syzbot
> >>> <syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
> >>>>
> >>>> Hello,
> >>>>
> >>>> syzbot found the following issue on:
> >>>>
> >>>> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
> >>>> git tree: upstream
> >>>> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
> >>>> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
> >>>> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
> >>>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> >>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
> >>>>
> >>>> Downloadable assets:
> >>>> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
> >>>> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
> >>>> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
> >>>>
> >>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> >>>> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
> >>>>
> >>>> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
> >>>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
> >>>> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
> >>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> >>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> >>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> >>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> >>>>
> >>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> >>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> >>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> >>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> >>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> >>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> >>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> >>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>>> Call Trace:
> >>>> <TASK>
> >>>> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
> >>>> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
> >>>> __kernel_write+0xf6/0x140 fs/read_write.c:632
> >>>> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
> >>>> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
> >>>> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
> >>>> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
> >>>> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
> >>>> task_work_run+0x14e/0x250 kernel/task_work.c:239
> >>>> exit_task_work include/linux/task_work.h:43 [inline]
> >>>> do_exit+0xad8/0x2d70 kernel/exit.c:938
> >>>> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
> >>>> get_signal+0x2576/0x2610 kernel/signal.c:3017
> >>>> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
> >>>> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
> >>>> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
> >>>> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
> >>>> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
> >>>> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
> >>>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >>>> RIP: 0033:0x7fee3cb87a6a
> >>>> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
> >>>> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
> >>>> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
> >>>> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
> >>>> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
> >>>> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
> >>>> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
> >>>> </TASK>
> >>>> Modules linked in:
> >>>> ---[ end trace 0000000000000000 ]---
> >>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> >>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> >>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> >>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> >>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> >>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> >>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> >>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> >>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> >>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> >>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>>> ----------------
> >>>> Code disassembly (best guess), 1 bytes skipped:
> >>>> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
> >>>> 5: 0f 85 fe 02 00 00 jne 0x309
> >>>> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
> >>>> 12: 00
> >>>> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> >>>> 1a: fc ff df
> >>>> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
> >>>> 22: 48 89 fa mov %rdi,%rdx
> >>>> 25: 48 c1 ea 03 shr $0x3,%rdx
> >>>> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> >>>> 2d: 0f 85 cc 02 00 00 jne 0x2ff
> >>>> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
> >>>> 38: 48 rex.W
> >>>> 39: 8d .byte 0x8d
> >>>> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
> >>
> >> (...)
> >>
> >>> I thought acct(2) was only allowing regular files.
> >>>
> >>> acct_on() indeed has :
> >>>
> >>> if (!S_ISREG(file_inode(file)->i_mode)) {
> >>> kfree(acct);
> >>> filp_close(file, NULL);
> >>> return -EACCES;
> >>> }
> >>>
> >>> It seems there are other ways to call do_acct_process() targeting a sysfs file ?
If this is the case, can you point me to the place where this happens?
> >>
> >> Just to be sure I'm not misunderstanding your comment: do you mean that
> >> here, the issue is *not* in MPTCP code where we get the 'struct net'
> >> pointer via 'current->nsproxy->net_ns', but in the FS part, right?
> >>
> >> Here, we have an issue because 'current->nsproxy' is NULL, but is it
> >> normal? Or should we simply exit with an error if it is the case because
> >> we are in an exiting phase?
> >>
> >> I'm just a bit confused, because it looks like 'net' is retrieved from
> >> different places elsewhere when dealing with sysfs: some get it from
> >> 'current' like us, some assign 'net' to 'table->extra2', others get it
> >> from 'table->data' (via a container_of()), etc. Maybe we should not use
> >> 'current->nsproxy->net_ns' here then?
> >
> > I do think this is a bug in process accounting, not in networking.
> >
> > It might make sense to output a record on a regular file, but probably
> > not on any other files.
It for sure does not make sense to output a record on a sysctl file that
has a maxlen of just 3*sizeof(int) (kernel/acct.c:79).
> >
> > diff --git a/kernel/acct.c b/kernel/acct.c
> > index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
> > 100644
> > --- a/kernel/acct.c
> > +++ b/kernel/acct.c
> > @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
> > const struct cred *orig_cred;
> > struct file *file = acct->file;
> >
> > + if (S_ISREG(file_inode(file)->i_mode))
> > + return;
> > +
This seems like it does not handle the actual culprit which is. Why is
the sysctl file being used for the accounting.
> > /*
> > * Accounting records are not subject to resource limits.
> > */
>
> OK, thank you, that's clearer.
>
> So this is then more a question for Joel, right?
>
> Do you plan to send this patch to him?
>
> #syz set subsystems: fs
>
> Cheers,
> Matt
> --
> Sponsored by the NGI0 Core fund.
>
So what is happening is that:
1. The accounting file is set to a non-sysctl file.
2. And when accounting tries to write to this file, you get the
behaviour explained in this mail?
Please correct me if I have miss-read the situation.
Best
--
Joel Granados
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-06 13:32 ` Joel Granados
@ 2025-01-06 14:27 ` Matthieu Baerts
2025-01-06 15:27 ` Eric Dumazet
2025-01-08 14:37 ` Joel Granados
0 siblings, 2 replies; 22+ messages in thread
From: Matthieu Baerts @ 2025-01-06 14:27 UTC (permalink / raw)
To: Joel Granados, Eric Dumazet, Al Viro
Cc: davem, geliang, horms, kuba, linux-kernel, martineau, mptcp,
netdev, pabeni, syzkaller-bugs, syzbot
Hi Joel, Eric, Al,
On 06/01/2025 14:32, Joel Granados wrote:
> On Sat, Jan 04, 2025 at 08:11:52PM +0100, Matthieu Baerts wrote:
>> Hi Eric,
>>
>> (+cc Joel)
>>
>> Thank you for your reply!
>>
>> On 04/01/2025 19:53, Eric Dumazet wrote:
>>> On Sat, Jan 4, 2025 at 7:38 PM Matthieu Baerts <matttbe@kernel.org> wrote:
>>>>
>>>> Hi Eric,
>>>>
>>>> Thank you for the bug report!
>>>>
>>>> On 02/01/2025 16:21, Eric Dumazet wrote:
>>>>> On Thu, Jan 2, 2025 at 3:12 PM syzbot
>>>>> <syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
>>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> syzbot found the following issue on:
>>>>>>
>>>>>> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
>>>>>> git tree: upstream
>>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
>>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
>>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
>>>>>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>>>>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
>>>>>>
>>>>>> Downloadable assets:
>>>>>> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
>>>>>> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
>>>>>> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
>>>>>>
>>>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>>>>> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
>>>>>>
>>>>>> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
>>>>>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
>>>>>> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
>>>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
>>>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
>>>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
>>>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>>>>>>
>>>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
>>>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
>>>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
>>>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
>>>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
>>>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
>>>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
>>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>>> Call Trace:
>>>>>> <TASK>
>>>>>> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
>>>>>> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
>>>>>> __kernel_write+0xf6/0x140 fs/read_write.c:632
>>>>>> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
>>>>>> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
>>>>>> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
>>>>>> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
>>>>>> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
>>>>>> task_work_run+0x14e/0x250 kernel/task_work.c:239
>>>>>> exit_task_work include/linux/task_work.h:43 [inline]
>>>>>> do_exit+0xad8/0x2d70 kernel/exit.c:938
>>>>>> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
>>>>>> get_signal+0x2576/0x2610 kernel/signal.c:3017
>>>>>> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
>>>>>> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
>>>>>> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
>>>>>> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
>>>>>> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
>>>>>> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
>>>>>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>>>>> RIP: 0033:0x7fee3cb87a6a
>>>>>> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
>>>>>> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
>>>>>> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
>>>>>> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
>>>>>> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
>>>>>> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
>>>>>> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
>>>>>> </TASK>
>>>>>> Modules linked in:
>>>>>> ---[ end trace 0000000000000000 ]---
>>>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
>>>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
>>>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>>>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
>>>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
>>>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
>>>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
>>>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
>>>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
>>>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
>>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>>> ----------------
>>>>>> Code disassembly (best guess), 1 bytes skipped:
>>>>>> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
>>>>>> 5: 0f 85 fe 02 00 00 jne 0x309
>>>>>> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
>>>>>> 12: 00
>>>>>> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
>>>>>> 1a: fc ff df
>>>>>> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
>>>>>> 22: 48 89 fa mov %rdi,%rdx
>>>>>> 25: 48 c1 ea 03 shr $0x3,%rdx
>>>>>> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
>>>>>> 2d: 0f 85 cc 02 00 00 jne 0x2ff
>>>>>> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
>>>>>> 38: 48 rex.W
>>>>>> 39: 8d .byte 0x8d
>>>>>> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
>>>>
>>>> (...)
>>>>
>>>>> I thought acct(2) was only allowing regular files.
>>>>>
>>>>> acct_on() indeed has :
>>>>>
>>>>> if (!S_ISREG(file_inode(file)->i_mode)) {
>>>>> kfree(acct);
>>>>> filp_close(file, NULL);
>>>>> return -EACCES;
>>>>> }
>>>>>
>>>>> It seems there are other ways to call do_acct_process() targeting a sysfs file ?
> If this is the case, can you point me to the place where this happens?
>
>>>>
>>>> Just to be sure I'm not misunderstanding your comment: do you mean that
>>>> here, the issue is *not* in MPTCP code where we get the 'struct net'
>>>> pointer via 'current->nsproxy->net_ns', but in the FS part, right?
>>>>
>>>> Here, we have an issue because 'current->nsproxy' is NULL, but is it
>>>> normal? Or should we simply exit with an error if it is the case because
>>>> we are in an exiting phase?
>>>>
>>>> I'm just a bit confused, because it looks like 'net' is retrieved from
>>>> different places elsewhere when dealing with sysfs: some get it from
>>>> 'current' like us, some assign 'net' to 'table->extra2', others get it
>>>> from 'table->data' (via a container_of()), etc. Maybe we should not use
>>>> 'current->nsproxy->net_ns' here then?
>>>
>>> I do think this is a bug in process accounting, not in networking.
>>>
>>> It might make sense to output a record on a regular file, but probably
>>> not on any other files.
> It for sure does not make sense to output a record on a sysctl file that
> has a maxlen of just 3*sizeof(int) (kernel/acct.c:79).
>
>>>
>>> diff --git a/kernel/acct.c b/kernel/acct.c
>>> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
>>> 100644
>>> --- a/kernel/acct.c
>>> +++ b/kernel/acct.c
>>> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
>>> const struct cred *orig_cred;
>>> struct file *file = acct->file;
>>>
>>> + if (S_ISREG(file_inode(file)->i_mode))
>>> + return;
>>> +
> This seems like it does not handle the actual culprit which is. Why is
> the sysctl file being used for the accounting.
>
>>> /*
>>> * Accounting records are not subject to resource limits.
>>> */
>>
>> OK, thank you, that's clearer.
>>
>> So this is then more a question for Joel, right?
>>
>> Do you plan to send this patch to him?
>>
>> #syz set subsystems: fs
>>
>> Cheers,
>> Matt
>> --
>> Sponsored by the NGI0 Core fund.
>>
>
> So what is happening is that:
> 1. The accounting file is set to a non-sysctl file.
> 2. And when accounting tries to write to this file, you get the
> behaviour explained in this mail?
>
> Please correct me if I have miss-read the situation.
@Joel: Thank you for your reply!
I'm sorry, I'm not sure whether I can help here. I hope Eric and/or Al
can jump in.
What I can say is that the original issue has been found by syzbot, and
the reproducer [1] shows that 3 syscalls have been used:
- openat('/proc/sys/net/mptcp/scheduler')
- mprotect()
- acct()
Please also note that the conversation continued in a sub-tread where
you are not in the Cc list, see [2]. In short, Eric suggested another
patch only for sysfs, and Al recommended dropping the use of
'current->nsproxy'.
On my side, I'm looking at dropping the use of 'current->nsproxy' in
sysctl callbacks. I guess such patches will be seen as fixes, except if
Eric's new patch is enough for stable?
[1] https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
[2]
https://lore.kernel.org/netdev/67769ecb.050a0220.3a8527.003f.GAE@google.com/T/#m862d0913ebfcec5e462a9c33b47bc3f6440a2900
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-06 14:27 ` Matthieu Baerts
@ 2025-01-06 15:27 ` Eric Dumazet
2025-01-06 15:34 ` Matthieu Baerts
2025-01-08 14:37 ` Joel Granados
1 sibling, 1 reply; 22+ messages in thread
From: Eric Dumazet @ 2025-01-06 15:27 UTC (permalink / raw)
To: Matthieu Baerts
Cc: Joel Granados, Al Viro, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Mon, Jan 6, 2025 at 3:27 PM Matthieu Baerts <matttbe@kernel.org> wrote:
>
> Hi Joel, Eric, Al,
>
> On 06/01/2025 14:32, Joel Granados wrote:
> > On Sat, Jan 04, 2025 at 08:11:52PM +0100, Matthieu Baerts wrote:
> >> Hi Eric,
> >>
> >> (+cc Joel)
> >>
> >> Thank you for your reply!
> >>
> >> On 04/01/2025 19:53, Eric Dumazet wrote:
> >>> On Sat, Jan 4, 2025 at 7:38 PM Matthieu Baerts <matttbe@kernel.org> wrote:
> >>>>
> >>>> Hi Eric,
> >>>>
> >>>> Thank you for the bug report!
> >>>>
> >>>> On 02/01/2025 16:21, Eric Dumazet wrote:
> >>>>> On Thu, Jan 2, 2025 at 3:12 PM syzbot
> >>>>> <syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
> >>>>>>
> >>>>>> Hello,
> >>>>>>
> >>>>>> syzbot found the following issue on:
> >>>>>>
> >>>>>> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
> >>>>>> git tree: upstream
> >>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
> >>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
> >>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
> >>>>>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> >>>>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
> >>>>>>
> >>>>>> Downloadable assets:
> >>>>>> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
> >>>>>> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
> >>>>>> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
> >>>>>>
> >>>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> >>>>>> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
> >>>>>>
> >>>>>> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
> >>>>>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
> >>>>>> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
> >>>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> >>>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> >>>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> >>>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> >>>>>>
> >>>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> >>>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> >>>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> >>>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> >>>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> >>>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> >>>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> >>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>>>>> Call Trace:
> >>>>>> <TASK>
> >>>>>> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
> >>>>>> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
> >>>>>> __kernel_write+0xf6/0x140 fs/read_write.c:632
> >>>>>> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
> >>>>>> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
> >>>>>> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
> >>>>>> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
> >>>>>> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
> >>>>>> task_work_run+0x14e/0x250 kernel/task_work.c:239
> >>>>>> exit_task_work include/linux/task_work.h:43 [inline]
> >>>>>> do_exit+0xad8/0x2d70 kernel/exit.c:938
> >>>>>> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
> >>>>>> get_signal+0x2576/0x2610 kernel/signal.c:3017
> >>>>>> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
> >>>>>> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
> >>>>>> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
> >>>>>> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
> >>>>>> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
> >>>>>> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
> >>>>>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >>>>>> RIP: 0033:0x7fee3cb87a6a
> >>>>>> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
> >>>>>> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
> >>>>>> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
> >>>>>> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
> >>>>>> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
> >>>>>> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
> >>>>>> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
> >>>>>> </TASK>
> >>>>>> Modules linked in:
> >>>>>> ---[ end trace 0000000000000000 ]---
> >>>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> >>>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> >>>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> >>>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> >>>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> >>>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> >>>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> >>>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> >>>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> >>>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> >>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>>>>> ----------------
> >>>>>> Code disassembly (best guess), 1 bytes skipped:
> >>>>>> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
> >>>>>> 5: 0f 85 fe 02 00 00 jne 0x309
> >>>>>> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
> >>>>>> 12: 00
> >>>>>> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> >>>>>> 1a: fc ff df
> >>>>>> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
> >>>>>> 22: 48 89 fa mov %rdi,%rdx
> >>>>>> 25: 48 c1 ea 03 shr $0x3,%rdx
> >>>>>> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> >>>>>> 2d: 0f 85 cc 02 00 00 jne 0x2ff
> >>>>>> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
> >>>>>> 38: 48 rex.W
> >>>>>> 39: 8d .byte 0x8d
> >>>>>> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
> >>>>
> >>>> (...)
> >>>>
> >>>>> I thought acct(2) was only allowing regular files.
> >>>>>
> >>>>> acct_on() indeed has :
> >>>>>
> >>>>> if (!S_ISREG(file_inode(file)->i_mode)) {
> >>>>> kfree(acct);
> >>>>> filp_close(file, NULL);
> >>>>> return -EACCES;
> >>>>> }
> >>>>>
> >>>>> It seems there are other ways to call do_acct_process() targeting a sysfs file ?
> > If this is the case, can you point me to the place where this happens?
> >
> >>>>
> >>>> Just to be sure I'm not misunderstanding your comment: do you mean that
> >>>> here, the issue is *not* in MPTCP code where we get the 'struct net'
> >>>> pointer via 'current->nsproxy->net_ns', but in the FS part, right?
> >>>>
> >>>> Here, we have an issue because 'current->nsproxy' is NULL, but is it
> >>>> normal? Or should we simply exit with an error if it is the case because
> >>>> we are in an exiting phase?
> >>>>
> >>>> I'm just a bit confused, because it looks like 'net' is retrieved from
> >>>> different places elsewhere when dealing with sysfs: some get it from
> >>>> 'current' like us, some assign 'net' to 'table->extra2', others get it
> >>>> from 'table->data' (via a container_of()), etc. Maybe we should not use
> >>>> 'current->nsproxy->net_ns' here then?
> >>>
> >>> I do think this is a bug in process accounting, not in networking.
> >>>
> >>> It might make sense to output a record on a regular file, but probably
> >>> not on any other files.
> > It for sure does not make sense to output a record on a sysctl file that
> > has a maxlen of just 3*sizeof(int) (kernel/acct.c:79).
> >
> >>>
> >>> diff --git a/kernel/acct.c b/kernel/acct.c
> >>> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
> >>> 100644
> >>> --- a/kernel/acct.c
> >>> +++ b/kernel/acct.c
> >>> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
> >>> const struct cred *orig_cred;
> >>> struct file *file = acct->file;
> >>>
> >>> + if (S_ISREG(file_inode(file)->i_mode))
> >>> + return;
> >>> +
> > This seems like it does not handle the actual culprit which is. Why is
> > the sysctl file being used for the accounting.
> >
> >>> /*
> >>> * Accounting records are not subject to resource limits.
> >>> */
> >>
> >> OK, thank you, that's clearer.
> >>
> >> So this is then more a question for Joel, right?
> >>
> >> Do you plan to send this patch to him?
> >>
> >> #syz set subsystems: fs
> >>
> >> Cheers,
> >> Matt
> >> --
> >> Sponsored by the NGI0 Core fund.
> >>
> >
> > So what is happening is that:
> > 1. The accounting file is set to a non-sysctl file.
> > 2. And when accounting tries to write to this file, you get the
> > behaviour explained in this mail?
> >
> > Please correct me if I have miss-read the situation.
>
> @Joel: Thank you for your reply!
>
> I'm sorry, I'm not sure whether I can help here. I hope Eric and/or Al
> can jump in.
>
> What I can say is that the original issue has been found by syzbot, and
> the reproducer [1] shows that 3 syscalls have been used:
> - openat('/proc/sys/net/mptcp/scheduler')
> - mprotect()
> - acct()
>
> Please also note that the conversation continued in a sub-tread where
> you are not in the Cc list, see [2]. In short, Eric suggested another
> patch only for sysfs, and Al recommended dropping the use of
> 'current->nsproxy'.
>
> On my side, I'm looking at dropping the use of 'current->nsproxy' in
> sysctl callbacks. I guess such patches will be seen as fixes, except if
> Eric's new patch is enough for stable?
It might be less risky in terms of backports to patch mptcp and others.
Ie just use Al suggestion.
Thanks !
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-06 15:27 ` Eric Dumazet
@ 2025-01-06 15:34 ` Matthieu Baerts
0 siblings, 0 replies; 22+ messages in thread
From: Matthieu Baerts @ 2025-01-06 15:34 UTC (permalink / raw)
To: Eric Dumazet
Cc: Joel Granados, Al Viro, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
Hi Eric,
Thank you for your reply!
On 06/01/2025 16:27, Eric Dumazet wrote:
> On Mon, Jan 6, 2025 at 3:27 PM Matthieu Baerts <matttbe@kernel.org> wrote:
>>
>> Hi Joel, Eric, Al,
>>
>> On 06/01/2025 14:32, Joel Granados wrote:
>>> On Sat, Jan 04, 2025 at 08:11:52PM +0100, Matthieu Baerts wrote:
>>>> Hi Eric,
>>>>
>>>> (+cc Joel)
>>>>
>>>> Thank you for your reply!
>>>>
>>>> On 04/01/2025 19:53, Eric Dumazet wrote:
>>>>> On Sat, Jan 4, 2025 at 7:38 PM Matthieu Baerts <matttbe@kernel.org> wrote:
>>>>>>
>>>>>> Hi Eric,
>>>>>>
>>>>>> Thank you for the bug report!
>>>>>>
>>>>>> On 02/01/2025 16:21, Eric Dumazet wrote:
>>>>>>> On Thu, Jan 2, 2025 at 3:12 PM syzbot
>>>>>>> <syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
>>>>>>>>
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> syzbot found the following issue on:
>>>>>>>>
>>>>>>>> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
>>>>>>>> git tree: upstream
>>>>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
>>>>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
>>>>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
>>>>>>>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>>>>>>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
>>>>>>>>
>>>>>>>> Downloadable assets:
>>>>>>>> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
>>>>>>>> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
>>>>>>>> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
>>>>>>>>
>>>>>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>>>>>>> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
>>>>>>>>
>>>>>>>> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
>>>>>>>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
>>>>>>>> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
>>>>>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
>>>>>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
>>>>>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
>>>>>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>>>>>>>>
>>>>>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
>>>>>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
>>>>>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
>>>>>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
>>>>>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
>>>>>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
>>>>>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
>>>>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>>>>> Call Trace:
>>>>>>>> <TASK>
>>>>>>>> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
>>>>>>>> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
>>>>>>>> __kernel_write+0xf6/0x140 fs/read_write.c:632
>>>>>>>> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
>>>>>>>> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
>>>>>>>> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
>>>>>>>> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
>>>>>>>> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
>>>>>>>> task_work_run+0x14e/0x250 kernel/task_work.c:239
>>>>>>>> exit_task_work include/linux/task_work.h:43 [inline]
>>>>>>>> do_exit+0xad8/0x2d70 kernel/exit.c:938
>>>>>>>> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
>>>>>>>> get_signal+0x2576/0x2610 kernel/signal.c:3017
>>>>>>>> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
>>>>>>>> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
>>>>>>>> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
>>>>>>>> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
>>>>>>>> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
>>>>>>>> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
>>>>>>>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>>>>>>> RIP: 0033:0x7fee3cb87a6a
>>>>>>>> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
>>>>>>>> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
>>>>>>>> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
>>>>>>>> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
>>>>>>>> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
>>>>>>>> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
>>>>>>>> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
>>>>>>>> </TASK>
>>>>>>>> Modules linked in:
>>>>>>>> ---[ end trace 0000000000000000 ]---
>>>>>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
>>>>>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
>>>>>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
>>>>>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
>>>>>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
>>>>>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
>>>>>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
>>>>>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
>>>>>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
>>>>>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
>>>>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>>>>> ----------------
>>>>>>>> Code disassembly (best guess), 1 bytes skipped:
>>>>>>>> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
>>>>>>>> 5: 0f 85 fe 02 00 00 jne 0x309
>>>>>>>> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
>>>>>>>> 12: 00
>>>>>>>> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
>>>>>>>> 1a: fc ff df
>>>>>>>> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
>>>>>>>> 22: 48 89 fa mov %rdi,%rdx
>>>>>>>> 25: 48 c1 ea 03 shr $0x3,%rdx
>>>>>>>> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
>>>>>>>> 2d: 0f 85 cc 02 00 00 jne 0x2ff
>>>>>>>> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
>>>>>>>> 38: 48 rex.W
>>>>>>>> 39: 8d .byte 0x8d
>>>>>>>> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
>>>>>>
>>>>>> (...)
>>>>>>
>>>>>>> I thought acct(2) was only allowing regular files.
>>>>>>>
>>>>>>> acct_on() indeed has :
>>>>>>>
>>>>>>> if (!S_ISREG(file_inode(file)->i_mode)) {
>>>>>>> kfree(acct);
>>>>>>> filp_close(file, NULL);
>>>>>>> return -EACCES;
>>>>>>> }
>>>>>>>
>>>>>>> It seems there are other ways to call do_acct_process() targeting a sysfs file ?
>>> If this is the case, can you point me to the place where this happens?
>>>
>>>>>>
>>>>>> Just to be sure I'm not misunderstanding your comment: do you mean that
>>>>>> here, the issue is *not* in MPTCP code where we get the 'struct net'
>>>>>> pointer via 'current->nsproxy->net_ns', but in the FS part, right?
>>>>>>
>>>>>> Here, we have an issue because 'current->nsproxy' is NULL, but is it
>>>>>> normal? Or should we simply exit with an error if it is the case because
>>>>>> we are in an exiting phase?
>>>>>>
>>>>>> I'm just a bit confused, because it looks like 'net' is retrieved from
>>>>>> different places elsewhere when dealing with sysfs: some get it from
>>>>>> 'current' like us, some assign 'net' to 'table->extra2', others get it
>>>>>> from 'table->data' (via a container_of()), etc. Maybe we should not use
>>>>>> 'current->nsproxy->net_ns' here then?
>>>>>
>>>>> I do think this is a bug in process accounting, not in networking.
>>>>>
>>>>> It might make sense to output a record on a regular file, but probably
>>>>> not on any other files.
>>> It for sure does not make sense to output a record on a sysctl file that
>>> has a maxlen of just 3*sizeof(int) (kernel/acct.c:79).
>>>
>>>>>
>>>>> diff --git a/kernel/acct.c b/kernel/acct.c
>>>>> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
>>>>> 100644
>>>>> --- a/kernel/acct.c
>>>>> +++ b/kernel/acct.c
>>>>> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
>>>>> const struct cred *orig_cred;
>>>>> struct file *file = acct->file;
>>>>>
>>>>> + if (S_ISREG(file_inode(file)->i_mode))
>>>>> + return;
>>>>> +
>>> This seems like it does not handle the actual culprit which is. Why is
>>> the sysctl file being used for the accounting.
>>>
>>>>> /*
>>>>> * Accounting records are not subject to resource limits.
>>>>> */
>>>>
>>>> OK, thank you, that's clearer.
>>>>
>>>> So this is then more a question for Joel, right?
>>>>
>>>> Do you plan to send this patch to him?
>>>>
>>>> #syz set subsystems: fs
>>>>
>>>> Cheers,
>>>> Matt
>>>> --
>>>> Sponsored by the NGI0 Core fund.
>>>>
>>>
>>> So what is happening is that:
>>> 1. The accounting file is set to a non-sysctl file.
>>> 2. And when accounting tries to write to this file, you get the
>>> behaviour explained in this mail?
>>>
>>> Please correct me if I have miss-read the situation.
>>
>> @Joel: Thank you for your reply!
>>
>> I'm sorry, I'm not sure whether I can help here. I hope Eric and/or Al
>> can jump in.
>>
>> What I can say is that the original issue has been found by syzbot, and
>> the reproducer [1] shows that 3 syscalls have been used:
>> - openat('/proc/sys/net/mptcp/scheduler')
>> - mprotect()
>> - acct()
>>
>> Please also note that the conversation continued in a sub-tread where
>> you are not in the Cc list, see [2]. In short, Eric suggested another
>> patch only for sysfs, and Al recommended dropping the use of
>> 'current->nsproxy'.
>>
>> On my side, I'm looking at dropping the use of 'current->nsproxy' in
>> sysctl callbacks. I guess such patches will be seen as fixes, except if
>> Eric's new patch is enough for stable?
>
> It might be less risky in terms of backports to patch mptcp and others.
>
> Ie just use Al suggestion.
Thank you, will do! In fact, I already modified the kernel on my side,
but it is hard for me to validate that for the moment: it is nice to
have many trees around, but less when they fall on cables :)
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: Re: [syzbot] [mptcp?] general protection fault in proc_scheduler
2025-01-06 14:27 ` Matthieu Baerts
2025-01-06 15:27 ` Eric Dumazet
@ 2025-01-08 14:37 ` Joel Granados
1 sibling, 0 replies; 22+ messages in thread
From: Joel Granados @ 2025-01-08 14:37 UTC (permalink / raw)
To: Matthieu Baerts
Cc: Eric Dumazet, Al Viro, davem, geliang, horms, kuba, linux-kernel,
martineau, mptcp, netdev, pabeni, syzkaller-bugs, syzbot
On Mon, Jan 06, 2025 at 03:27:47PM +0100, Matthieu Baerts wrote:
> Hi Joel, Eric, Al,
>
> On 06/01/2025 14:32, Joel Granados wrote:
> > On Sat, Jan 04, 2025 at 08:11:52PM +0100, Matthieu Baerts wrote:
> >> Hi Eric,
> >>
> >> (+cc Joel)
> >>
> >> Thank you for your reply!
> >>
> >> On 04/01/2025 19:53, Eric Dumazet wrote:
> >>> On Sat, Jan 4, 2025 at 7:38 PM Matthieu Baerts <matttbe@kernel.org> wrote:
> >>>>
> >>>> Hi Eric,
> >>>>
> >>>> Thank you for the bug report!
> >>>>
> >>>> On 02/01/2025 16:21, Eric Dumazet wrote:
> >>>>> On Thu, Jan 2, 2025 at 3:12 PM syzbot
> >>>>> <syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com> wrote:
> >>>>>>
> >>>>>> Hello,
> >>>>>>
> >>>>>> syzbot found the following issue on:
> >>>>>>
> >>>>>> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
> >>>>>> git tree: upstream
> >>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000
> >>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
> >>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1
> >>>>>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> >>>>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000
> >>>>>>
> >>>>>> Downloadable assets:
> >>>>>> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz
> >>>>>> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz
> >>>>>> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz
> >>>>>>
> >>>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> >>>>>> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com
> >>>>>>
> >>>>>> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI
> >>>>>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
> >>>>>> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0
> >>>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> >>>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> >>>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> >>>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> >>>>>>
> >>>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> >>>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> >>>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> >>>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> >>>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> >>>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> >>>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> >>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>>>>> Call Trace:
> >>>>>> <TASK>
> >>>>>> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601
> >>>>>> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612
> >>>>>> __kernel_write+0xf6/0x140 fs/read_write.c:632
> >>>>>> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539
> >>>>>> acct_pin_kill+0x2d/0x100 kernel/acct.c:192
> >>>>>> pin_kill+0x194/0x7c0 fs/fs_pin.c:44
> >>>>>> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81
> >>>>>> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366
> >>>>>> task_work_run+0x14e/0x250 kernel/task_work.c:239
> >>>>>> exit_task_work include/linux/task_work.h:43 [inline]
> >>>>>> do_exit+0xad8/0x2d70 kernel/exit.c:938
> >>>>>> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
> >>>>>> get_signal+0x2576/0x2610 kernel/signal.c:3017
> >>>>>> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
> >>>>>> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
> >>>>>> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
> >>>>>> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
> >>>>>> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
> >>>>>> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
> >>>>>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >>>>>> RIP: 0033:0x7fee3cb87a6a
> >>>>>> Code: Unable to access opcode bytes at 0x7fee3cb87a40.
> >>>>>> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037
> >>>>>> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a
> >>>>>> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
> >>>>>> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7
> >>>>>> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500
> >>>>>> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000
> >>>>>> </TASK>
> >>>>>> Modules linked in:
> >>>>>> ---[ end trace 0000000000000000 ]---
> >>>>>> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125
> >>>>>> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00
> >>>>>> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206
> >>>>>> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620
> >>>>>> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028
> >>>>>> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040
> >>>>>> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000
> >>>>>> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000
> >>>>>> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> >>>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>>>> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0
> >>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>>>>> ----------------
> >>>>>> Code disassembly (best guess), 1 bytes skipped:
> >>>>>> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
> >>>>>> 5: 0f 85 fe 02 00 00 jne 0x309
> >>>>>> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12
> >>>>>> 12: 00
> >>>>>> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> >>>>>> 1a: fc ff df
> >>>>>> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi
> >>>>>> 22: 48 89 fa mov %rdi,%rdx
> >>>>>> 25: 48 c1 ea 03 shr $0x3,%rdx
> >>>>>> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> >>>>>> 2d: 0f 85 cc 02 00 00 jne 0x2ff
> >>>>>> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15
> >>>>>> 38: 48 rex.W
> >>>>>> 39: 8d .byte 0x8d
> >>>>>> 3a: 84 24 c8 test %ah,(%rax,%rcx,8)
> >>>>
> >>>> (...)
> >>>>
> >>>>> I thought acct(2) was only allowing regular files.
> >>>>>
> >>>>> acct_on() indeed has :
> >>>>>
> >>>>> if (!S_ISREG(file_inode(file)->i_mode)) {
> >>>>> kfree(acct);
> >>>>> filp_close(file, NULL);
> >>>>> return -EACCES;
> >>>>> }
> >>>>>
> >>>>> It seems there are other ways to call do_acct_process() targeting a sysfs file ?
> > If this is the case, can you point me to the place where this happens?
> >
> >>>>
> >>>> Just to be sure I'm not misunderstanding your comment: do you mean that
> >>>> here, the issue is *not* in MPTCP code where we get the 'struct net'
> >>>> pointer via 'current->nsproxy->net_ns', but in the FS part, right?
> >>>>
> >>>> Here, we have an issue because 'current->nsproxy' is NULL, but is it
> >>>> normal? Or should we simply exit with an error if it is the case because
> >>>> we are in an exiting phase?
> >>>>
> >>>> I'm just a bit confused, because it looks like 'net' is retrieved from
> >>>> different places elsewhere when dealing with sysfs: some get it from
> >>>> 'current' like us, some assign 'net' to 'table->extra2', others get it
> >>>> from 'table->data' (via a container_of()), etc. Maybe we should not use
> >>>> 'current->nsproxy->net_ns' here then?
> >>>
> >>> I do think this is a bug in process accounting, not in networking.
> >>>
> >>> It might make sense to output a record on a regular file, but probably
> >>> not on any other files.
> > It for sure does not make sense to output a record on a sysctl file that
> > has a maxlen of just 3*sizeof(int) (kernel/acct.c:79).
> >
> >>>
> >>> diff --git a/kernel/acct.c b/kernel/acct.c
> >>> index 179848ad33e978a557ce695a0d6020aa169177c6..a211305cb930f6860d02de7f45ebd260ae03a604
> >>> 100644
> >>> --- a/kernel/acct.c
> >>> +++ b/kernel/acct.c
> >>> @@ -495,6 +495,9 @@ static void do_acct_process(struct bsd_acct_struct *acct)
> >>> const struct cred *orig_cred;
> >>> struct file *file = acct->file;
> >>>
> >>> + if (S_ISREG(file_inode(file)->i_mode))
> >>> + return;
> >>> +
> > This seems like it does not handle the actual culprit which is. Why is
> > the sysctl file being used for the accounting.
> >
> >>> /*
> >>> * Accounting records are not subject to resource limits.
> >>> */
> >>
> >> OK, thank you, that's clearer.
> >>
> >> So this is then more a question for Joel, right?
> >>
> >> Do you plan to send this patch to him?
> >>
> >> #syz set subsystems: fs
> >>
> >> Cheers,
> >> Matt
> >> --
> >> Sponsored by the NGI0 Core fund.
> >>
> >
> > So what is happening is that:
> > 1. The accounting file is set to a non-sysctl file.
> > 2. And when accounting tries to write to this file, you get the
> > behaviour explained in this mail?
> >
> > Please correct me if I have miss-read the situation.
>
> @Joel: Thank you for your reply!
>
> I'm sorry, I'm not sure whether I can help here. I hope Eric and/or Al
> can jump in.
>
> What I can say is that the original issue has been found by syzbot, and
> the reproducer [1] shows that 3 syscalls have been used:
> - openat('/proc/sys/net/mptcp/scheduler')
> - mprotect()
> - acct()
>
> Please also note that the conversation continued in a sub-tread where
> you are not in the Cc list, see [2]. In short, Eric suggested another
> patch only for sysfs, and Al recommended dropping the use of
> 'current->nsproxy'.
Perfect. Thx for the summary. I'll remove this thread from my radar as
it seems that a fix has already been found.
Best
--
Joel Granados
^ permalink raw reply [flat|nested] 22+ messages in thread
end of thread, other threads:[~2025-01-08 14:37 UTC | newest]
Thread overview: 22+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-01-02 14:12 [syzbot] [mptcp?] general protection fault in proc_scheduler syzbot
2025-01-02 15:21 ` Eric Dumazet
2025-01-04 18:38 ` Matthieu Baerts
2025-01-04 18:53 ` Eric Dumazet
2025-01-04 19:00 ` Al Viro
2025-01-04 19:11 ` Matthieu Baerts
2025-01-04 20:21 ` Al Viro
2025-01-05 8:32 ` Eric Dumazet
2025-01-05 11:29 ` Al Viro
2025-01-05 16:52 ` Eric Dumazet
2025-01-05 17:03 ` Matthieu Baerts
2025-01-05 19:54 ` Al Viro
2025-01-05 20:50 ` Al Viro
2025-01-05 21:11 ` Al Viro
2025-01-05 17:03 ` Matthieu Baerts
2025-01-04 19:11 ` Matthieu Baerts
2025-01-06 13:32 ` Joel Granados
2025-01-06 14:27 ` Matthieu Baerts
2025-01-06 15:27 ` Eric Dumazet
2025-01-06 15:34 ` Matthieu Baerts
2025-01-08 14:37 ` Joel Granados
2025-01-04 20:09 ` Al Viro
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