* [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit
@ 2023-08-06 23:23 syzbot
2023-08-07 6:40 ` Yonghong Song
0 siblings, 1 reply; 7+ messages in thread
From: syzbot @ 2023-08-06 23:23 UTC (permalink / raw)
To: andrii, ast, bpf, daniel, davem, eddyz87, haoluo, hawk,
john.fastabend, jolsa, kpsingh, kuba, linux-kernel, martin.lau,
netdev, sdf, song, syzkaller-bugs, yonghong.song
Hello,
syzbot found the following issue on:
HEAD commit: 25ad10658dc1 riscv, bpf: Adapt bpf trampoline to optimized..
git tree: bpf-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=147cbb29a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=8acaeb93ad7c6aaa
dashboard link: https://syzkaller.appspot.com/bug?extid=d61b595e9205573133b3
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=14d73ccea80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1276aedea80000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3d378cc13d42/disk-25ad1065.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/44580fd5d1af/vmlinux-25ad1065.xz
kernel image: https://storage.googleapis.com/syzbot-assets/840587618b41/bzImage-25ad1065.xz
The issue was bisected to:
commit 8100928c881482a73ed8bd499d602bab0fe55608
Author: Yonghong Song <yonghong.song@linux.dev>
Date: Fri Jul 28 01:12:02 2023 +0000
bpf: Support new sign-extension mov insns
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17970c5da80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=14570c5da80000
console output: https://syzkaller.appspot.com/x/log.txt?x=10570c5da80000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d61b595e9205573133b3@syzkaller.appspotmail.com
Fixes: 8100928c8814 ("bpf: Support new sign-extension mov insns")
general protection fault, probably for non-canonical address 0xdffffc0000000f4f: 0000 [#1] PREEMPT SMP KASAN
KASAN: probably user-memory-access in range [0x0000000000007a78-0x0000000000007a7f]
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.5.0-rc2-syzkaller-00619-g25ad10658dc1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
RIP: 0010:strnchr+0x25/0x80 lib/string.c:403
Code: 00 00 00 00 90 f3 0f 1e fa 53 48 01 fe 48 bb 00 00 00 00 00 fc ff df 48 83 ec 18 eb 28 48 89 f8 48 89 f9 48 c1 e8 03 83 e1 07 <0f> b6 04 18 38 c8 7f 04 84 c0 75 25 0f b6 07 38 d0 74 15 48 83 c7
RSP: 0018:ffffc90000177848 EFLAGS: 00010046
RAX: 0000000000000f4f RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000007a7b RDI: 0000000000007a78
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000007a78
R13: ffffc900001779b0 R14: 0000000000000000 R15: 0000000000000003
FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005611db5094b8 CR3: 0000000028ef0000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
bpf_bprintf_prepare+0x127/0x1490 kernel/bpf/helpers.c:823
____bpf_trace_printk kernel/trace/bpf_trace.c:385 [inline]
bpf_trace_printk+0xdb/0x180 kernel/trace/bpf_trace.c:375
bpf_prog_ebeed182d92b487f+0x38/0x3c
bpf_dispatcher_nop_func include/linux/bpf.h:1180 [inline]
__bpf_prog_run include/linux/filter.h:609 [inline]
bpf_prog_run include/linux/filter.h:616 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2269 [inline]
bpf_trace_run1+0x148/0x400 kernel/trace/bpf_trace.c:2307
__bpf_trace_rcu_utilization+0x8e/0xc0 include/trace/events/rcu.h:27
trace_rcu_utilization+0xcd/0x120 include/trace/events/rcu.h:27
rcu_note_context_switch+0x6c/0x1ac0 kernel/rcu/tree_plugin.h:318
__schedule+0x293/0x59f0 kernel/sched/core.c:6610
schedule_idle+0x5b/0x80 kernel/sched/core.c:6814
do_idle+0x288/0x3f0 kernel/sched/idle.c:310
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:379
start_secondary+0x200/0x290 arch/x86/kernel/smpboot.c:326
secondary_startup_64_no_verify+0x167/0x16b
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:strnchr+0x25/0x80 lib/string.c:403
Code: 00 00 00 00 90 f3 0f 1e fa 53 48 01 fe 48 bb 00 00 00 00 00 fc ff df 48 83 ec 18 eb 28 48 89 f8 48 89 f9 48 c1 e8 03 83 e1 07 <0f> b6 04 18 38 c8 7f 04 84 c0 75 25 0f b6 07 38 d0 74 15 48 83 c7
RSP: 0018:ffffc90000177848 EFLAGS: 00010046
RAX: 0000000000000f4f RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000007a7b RDI: 0000000000007a78
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000007a78
R13: ffffc900001779b0 R14: 0000000000000000 R15: 0000000000000003
FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005611db5094b8 CR3: 0000000028ef0000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 00 00 add %al,(%rax)
2: 00 00 add %al,(%rax)
4: 90 nop
5: f3 0f 1e fa endbr64
9: 53 push %rbx
a: 48 01 fe add %rdi,%rsi
d: 48 bb 00 00 00 00 00 movabs $0xdffffc0000000000,%rbx
14: fc ff df
17: 48 83 ec 18 sub $0x18,%rsp
1b: eb 28 jmp 0x45
1d: 48 89 f8 mov %rdi,%rax
20: 48 89 f9 mov %rdi,%rcx
23: 48 c1 e8 03 shr $0x3,%rax
27: 83 e1 07 and $0x7,%ecx
* 2a: 0f b6 04 18 movzbl (%rax,%rbx,1),%eax <-- trapping instruction
2e: 38 c8 cmp %cl,%al
30: 7f 04 jg 0x36
32: 84 c0 test %al,%al
34: 75 25 jne 0x5b
36: 0f b6 07 movzbl (%rdi),%eax
39: 38 d0 cmp %dl,%al
3b: 74 15 je 0x52
3d: 48 rex.W
3e: 83 .byte 0x83
3f: c7 .byte 0xc7
---
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.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
If the bug is already fixed, 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 change bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit
2023-08-06 23:23 [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit syzbot
@ 2023-08-07 6:40 ` Yonghong Song
2023-08-07 13:11 ` Eduard Zingerman
0 siblings, 1 reply; 7+ messages in thread
From: Yonghong Song @ 2023-08-07 6:40 UTC (permalink / raw)
To: syzbot, andrii, ast, bpf, daniel, davem, eddyz87, haoluo, hawk,
john.fastabend, jolsa, kpsingh, kuba, linux-kernel, martin.lau,
netdev, sdf, song, syzkaller-bugs
On 8/6/23 4:23 PM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 25ad10658dc1 riscv, bpf: Adapt bpf trampoline to optimized..
> git tree: bpf-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=147cbb29a80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8acaeb93ad7c6aaa
> dashboard link: https://syzkaller.appspot.com/bug?extid=d61b595e9205573133b3
> 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=14d73ccea80000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1276aedea80000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/3d378cc13d42/disk-25ad1065.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/44580fd5d1af/vmlinux-25ad1065.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/840587618b41/bzImage-25ad1065.xz
>
> The issue was bisected to:
>
> commit 8100928c881482a73ed8bd499d602bab0fe55608
> Author: Yonghong Song <yonghong.song@linux.dev>
> Date: Fri Jul 28 01:12:02 2023 +0000
>
> bpf: Support new sign-extension mov insns
Thanks for reporting. I will look into this ASAP.
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17970c5da80000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=14570c5da80000
> console output: https://syzkaller.appspot.com/x/log.txt?x=10570c5da80000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d61b595e9205573133b3@syzkaller.appspotmail.com
> Fixes: 8100928c8814 ("bpf: Support new sign-extension mov insns")
>
> general protection fault, probably for non-canonical address 0xdffffc0000000f4f: 0000 [#1] PREEMPT SMP KASAN
> KASAN: probably user-memory-access in range [0x0000000000007a78-0x0000000000007a7f]
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.5.0-rc2-syzkaller-00619-g25ad10658dc1 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
> RIP: 0010:strnchr+0x25/0x80 lib/string.c:403
> Code: 00 00 00 00 90 f3 0f 1e fa 53 48 01 fe 48 bb 00 00 00 00 00 fc ff df 48 83 ec 18 eb 28 48 89 f8 48 89 f9 48 c1 e8 03 83 e1 07 <0f> b6 04 18 38 c8 7f 04 84 c0 75 25 0f b6 07 38 d0 74 15 48 83 c7
> RSP: 0018:ffffc90000177848 EFLAGS: 00010046
> RAX: 0000000000000f4f RBX: dffffc0000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000007a7b RDI: 0000000000007a78
> RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000007a78
> R13: ffffc900001779b0 R14: 0000000000000000 R15: 0000000000000003
> FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005611db5094b8 CR3: 0000000028ef0000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> bpf_bprintf_prepare+0x127/0x1490 kernel/bpf/helpers.c:823
> ____bpf_trace_printk kernel/trace/bpf_trace.c:385 [inline]
> bpf_trace_printk+0xdb/0x180 kernel/trace/bpf_trace.c:375
> bpf_prog_ebeed182d92b487f+0x38/0x3c
> bpf_dispatcher_nop_func include/linux/bpf.h:1180 [inline]
> __bpf_prog_run include/linux/filter.h:609 [inline]
> bpf_prog_run include/linux/filter.h:616 [inline]
> __bpf_trace_run kernel/trace/bpf_trace.c:2269 [inline]
> bpf_trace_run1+0x148/0x400 kernel/trace/bpf_trace.c:2307
> __bpf_trace_rcu_utilization+0x8e/0xc0 include/trace/events/rcu.h:27
> trace_rcu_utilization+0xcd/0x120 include/trace/events/rcu.h:27
> rcu_note_context_switch+0x6c/0x1ac0 kernel/rcu/tree_plugin.h:318
> __schedule+0x293/0x59f0 kernel/sched/core.c:6610
> schedule_idle+0x5b/0x80 kernel/sched/core.c:6814
> do_idle+0x288/0x3f0 kernel/sched/idle.c:310
> cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:379
> start_secondary+0x200/0x290 arch/x86/kernel/smpboot.c:326
> secondary_startup_64_no_verify+0x167/0x16b
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:strnchr+0x25/0x80 lib/string.c:403
> Code: 00 00 00 00 90 f3 0f 1e fa 53 48 01 fe 48 bb 00 00 00 00 00 fc ff df 48 83 ec 18 eb 28 48 89 f8 48 89 f9 48 c1 e8 03 83 e1 07 <0f> b6 04 18 38 c8 7f 04 84 c0 75 25 0f b6 07 38 d0 74 15 48 83 c7
> RSP: 0018:ffffc90000177848 EFLAGS: 00010046
>
> RAX: 0000000000000f4f RBX: dffffc0000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000007a7b RDI: 0000000000007a78
> RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000007a78
> R13: ffffc900001779b0 R14: 0000000000000000 R15: 0000000000000003
> FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005611db5094b8 CR3: 0000000028ef0000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
> 0: 00 00 add %al,(%rax)
> 2: 00 00 add %al,(%rax)
> 4: 90 nop
> 5: f3 0f 1e fa endbr64
> 9: 53 push %rbx
> a: 48 01 fe add %rdi,%rsi
> d: 48 bb 00 00 00 00 00 movabs $0xdffffc0000000000,%rbx
> 14: fc ff df
> 17: 48 83 ec 18 sub $0x18,%rsp
> 1b: eb 28 jmp 0x45
> 1d: 48 89 f8 mov %rdi,%rax
> 20: 48 89 f9 mov %rdi,%rcx
> 23: 48 c1 e8 03 shr $0x3,%rax
> 27: 83 e1 07 and $0x7,%ecx
> * 2a: 0f b6 04 18 movzbl (%rax,%rbx,1),%eax <-- trapping instruction
> 2e: 38 c8 cmp %cl,%al
> 30: 7f 04 jg 0x36
> 32: 84 c0 test %al,%al
> 34: 75 25 jne 0x5b
> 36: 0f b6 07 movzbl (%rdi),%eax
> 39: 38 d0 cmp %dl,%al
> 3b: 74 15 je 0x52
> 3d: 48 rex.W
> 3e: 83 .byte 0x83
> 3f: c7 .byte 0xc7
>
>
[...]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit
2023-08-07 6:40 ` Yonghong Song
@ 2023-08-07 13:11 ` Eduard Zingerman
2023-08-07 13:48 ` Eduard Zingerman
2023-08-07 14:40 ` Yonghong Song
0 siblings, 2 replies; 7+ messages in thread
From: Eduard Zingerman @ 2023-08-07 13:11 UTC (permalink / raw)
To: yonghong.song, syzbot, andrii, ast, bpf, daniel, davem, haoluo,
hawk, john.fastabend, jolsa, kpsingh, kuba, linux-kernel,
martin.lau, netdev, sdf, song, syzkaller-bugs
On Sun, 2023-08-06 at 23:40 -0700, Yonghong Song wrote:
>
> On 8/6/23 4:23 PM, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 25ad10658dc1 riscv, bpf: Adapt bpf trampoline to optimized..
> > git tree: bpf-next
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=147cbb29a80000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=8acaeb93ad7c6aaa
> > dashboard link: https://syzkaller.appspot.com/bug?extid=d61b595e9205573133b3
> > 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=14d73ccea80000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1276aedea80000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/3d378cc13d42/disk-25ad1065.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/44580fd5d1af/vmlinux-25ad1065.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/840587618b41/bzImage-25ad1065.xz
> >
> > The issue was bisected to:
> >
> > commit 8100928c881482a73ed8bd499d602bab0fe55608
> > Author: Yonghong Song <yonghong.song@linux.dev>
> > Date: Fri Jul 28 01:12:02 2023 +0000
> >
> > bpf: Support new sign-extension mov insns
>
> Thanks for reporting. I will look into this ASAP.
Hi Yonghong,
I guess it's your night and my morning, so I did some initial assessment.
The BPF program being loaded is:
0 : (62) *(u32 *)(r10 -8) = 553656332
1 : (bf) r1 = (s16)r10
2 : (07) r1 += -8
3 : (b7) r2 = 3
4 : (bd) if r2 <= r1 goto pc+0
5 : (85) call bpf_trace_printk#6
6 : (b7) r0 = 0
7 : (95) exit
(Note: when using bpftool (prog dump xlated id <some-id>) the disassembly
of the instruction #1 is incorrectly printed as "1: (bf) r1 = r10")
The error occurs when instruction #5 (call to printk) is executed.
An incorrect address for the format string is passed to printk.
Disassembly of the jited program looks as follows:
$ bpftool prog dump jited id <some-id>
bpf_prog_ebeed182d92b487f:
0: nopl (%rax,%rax)
5: nop
7: pushq %rbp
8: movq %rsp, %rbp
b: subq $8, %rsp
12: movl $553656332, -8(%rbp)
19: movswq %bp, %rdi ; <---- Note movswq %bp !
1d: addq $-8, %rdi
21: movl $3, %esi
26: cmpq %rdi, %rsi
29: jbe 0x2b
2b: callq 0xffffffffe11c484c
30: xorl %eax, %eax
32: leave
33: retq
Note jit instruction #19 corresponding to BPF instruction #1, which
loads truncated and sign-extended value of %rbp's first byte as an
address of format string.
Here is how verifier log looks for (slightly modified) program:
func#0 @0
0: R1=ctx(off=0,imm=0) R10=fp0
; asm volatile (" \n\
0: (b7) r1 = 553656332 ; R1_w=553656332
1: (63) *(u32 *)(r10 -8) = r1 ; R1_w=553656332 R10=fp0 fp-8=553656332
2: (bf) r1 = (s16)r10 ; R1_w=fp0 R10=fp0
3: (07) r1 += -8 ; R1_w=fp-8
4: (b7) r2 = 3 ; R2_w=3
5: (bd) if r2 <= r1 goto pc+0 ; R1_w=fp-8 R2_w=3
6: (85) call bpf_trace_printk#6
mark_precise: frame0: last_idx 6 first_idx 0 subseq_idx -1
...
mark_precise: frame0: falling back to forcing all scalars precise
7: R0=scalar()
7: (b7) r0 = 0 ; R0_w=0
8: (95) exit
from 5 to 6: R1_w=fp-8 R2_w=3 R10=fp0 fp-8=553656332
6: (85) call bpf_trace_printk#6
mark_precise: frame0: last_idx 6 first_idx 0 subseq_idx -1
...
mark_precise: frame0: falling back to forcing all scalars precise
7: safe
Note the following line:
2: (bf) r1 = (s16)r10 ; R1_w=fp0 R10=fp0
Verifier incorrectly marked r1 as fp0, hence not noticing the problem
with address passed to printk.
Thanks,
Eduard.
> >
> > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17970c5da80000
> > final oops: https://syzkaller.appspot.com/x/report.txt?x=14570c5da80000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=10570c5da80000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+d61b595e9205573133b3@syzkaller.appspotmail.com
> > Fixes: 8100928c8814 ("bpf: Support new sign-extension mov insns")
> >
> > general protection fault, probably for non-canonical address 0xdffffc0000000f4f: 0000 [#1] PREEMPT SMP KASAN
> > KASAN: probably user-memory-access in range [0x0000000000007a78-0x0000000000007a7f]
> > CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.5.0-rc2-syzkaller-00619-g25ad10658dc1 #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
> > RIP: 0010:strnchr+0x25/0x80 lib/string.c:403
> > Code: 00 00 00 00 90 f3 0f 1e fa 53 48 01 fe 48 bb 00 00 00 00 00 fc ff df 48 83 ec 18 eb 28 48 89 f8 48 89 f9 48 c1 e8 03 83 e1 07 <0f> b6 04 18 38 c8 7f 04 84 c0 75 25 0f b6 07 38 d0 74 15 48 83 c7
> > RSP: 0018:ffffc90000177848 EFLAGS: 00010046
> > RAX: 0000000000000f4f RBX: dffffc0000000000 RCX: 0000000000000000
> > RDX: 0000000000000000 RSI: 0000000000007a7b RDI: 0000000000007a78
> > RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
> > R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000007a78
> > R13: ffffc900001779b0 R14: 0000000000000000 R15: 0000000000000003
> > FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00005611db5094b8 CR3: 0000000028ef0000 CR4: 00000000003506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> > <TASK>
> > bpf_bprintf_prepare+0x127/0x1490 kernel/bpf/helpers.c:823
> > ____bpf_trace_printk kernel/trace/bpf_trace.c:385 [inline]
> > bpf_trace_printk+0xdb/0x180 kernel/trace/bpf_trace.c:375
> > bpf_prog_ebeed182d92b487f+0x38/0x3c
> > bpf_dispatcher_nop_func include/linux/bpf.h:1180 [inline]
> > __bpf_prog_run include/linux/filter.h:609 [inline]
> > bpf_prog_run include/linux/filter.h:616 [inline]
> > __bpf_trace_run kernel/trace/bpf_trace.c:2269 [inline]
> > bpf_trace_run1+0x148/0x400 kernel/trace/bpf_trace.c:2307
> > __bpf_trace_rcu_utilization+0x8e/0xc0 include/trace/events/rcu.h:27
> > trace_rcu_utilization+0xcd/0x120 include/trace/events/rcu.h:27
> > rcu_note_context_switch+0x6c/0x1ac0 kernel/rcu/tree_plugin.h:318
> > __schedule+0x293/0x59f0 kernel/sched/core.c:6610
> > schedule_idle+0x5b/0x80 kernel/sched/core.c:6814
> > do_idle+0x288/0x3f0 kernel/sched/idle.c:310
> > cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:379
> > start_secondary+0x200/0x290 arch/x86/kernel/smpboot.c:326
> > secondary_startup_64_no_verify+0x167/0x16b
> > </TASK>
> > Modules linked in:
> > ---[ end trace 0000000000000000 ]---
> > RIP: 0010:strnchr+0x25/0x80 lib/string.c:403
> > Code: 00 00 00 00 90 f3 0f 1e fa 53 48 01 fe 48 bb 00 00 00 00 00 fc ff df 48 83 ec 18 eb 28 48 89 f8 48 89 f9 48 c1 e8 03 83 e1 07 <0f> b6 04 18 38 c8 7f 04 84 c0 75 25 0f b6 07 38 d0 74 15 48 83 c7
> > RSP: 0018:ffffc90000177848 EFLAGS: 00010046
> >
> > RAX: 0000000000000f4f RBX: dffffc0000000000 RCX: 0000000000000000
> > RDX: 0000000000000000 RSI: 0000000000007a7b RDI: 0000000000007a78
> > RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
> > R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000007a78
> > R13: ffffc900001779b0 R14: 0000000000000000 R15: 0000000000000003
> > FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00005611db5094b8 CR3: 0000000028ef0000 CR4: 00000000003506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > ----------------
> > Code disassembly (best guess):
> > 0: 00 00 add %al,(%rax)
> > 2: 00 00 add %al,(%rax)
> > 4: 90 nop
> > 5: f3 0f 1e fa endbr64
> > 9: 53 push %rbx
> > a: 48 01 fe add %rdi,%rsi
> > d: 48 bb 00 00 00 00 00 movabs $0xdffffc0000000000,%rbx
> > 14: fc ff df
> > 17: 48 83 ec 18 sub $0x18,%rsp
> > 1b: eb 28 jmp 0x45
> > 1d: 48 89 f8 mov %rdi,%rax
> > 20: 48 89 f9 mov %rdi,%rcx
> > 23: 48 c1 e8 03 shr $0x3,%rax
> > 27: 83 e1 07 and $0x7,%ecx
> > * 2a: 0f b6 04 18 movzbl (%rax,%rbx,1),%eax <-- trapping instruction
> > 2e: 38 c8 cmp %cl,%al
> > 30: 7f 04 jg 0x36
> > 32: 84 c0 test %al,%al
> > 34: 75 25 jne 0x5b
> > 36: 0f b6 07 movzbl (%rdi),%eax
> > 39: 38 d0 cmp %dl,%al
> > 3b: 74 15 je 0x52
> > 3d: 48 rex.W
> > 3e: 83 .byte 0x83
> > 3f: c7 .byte 0xc7
> >
> >
> [...]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit
2023-08-07 13:11 ` Eduard Zingerman
@ 2023-08-07 13:48 ` Eduard Zingerman
2023-08-07 14:40 ` Yonghong Song
1 sibling, 0 replies; 7+ messages in thread
From: Eduard Zingerman @ 2023-08-07 13:48 UTC (permalink / raw)
To: yonghong.song, syzbot, andrii, ast, bpf, daniel, davem, haoluo,
hawk, john.fastabend, jolsa, kpsingh, kuba, linux-kernel,
martin.lau, netdev, sdf, song, syzkaller-bugs
On Mon, 2023-08-07 at 16:11 +0300, Eduard Zingerman wrote:
[...]
> $ bpftool prog dump jited id <some-id>
> bpf_prog_ebeed182d92b487f:
> 0: nopl (%rax,%rax)
> 5: nop
> 7: pushq %rbp
> 8: movq %rsp, %rbp
> b: subq $8, %rsp
> 12: movl $553656332, -8(%rbp)
> 19: movswq %bp, %rdi ; <---- Note movswq %bp !
> 1d: addq $-8, %rdi
> 21: movl $3, %esi
> 26: cmpq %rdi, %rsi
> 29: jbe 0x2b
> 2b: callq 0xffffffffe11c484c
> 30: xorl %eax, %eax
> 32: leave
> 33: retq
>
> Note jit instruction #19 corresponding to BPF instruction #1, which
> loads truncated and sign-extended value of %rbp's first byte as an
> address of format string.
Correction: sign-extended value of %rbp's first *two* bytes,
disassembly with opcodes:
19: movswq %bp, %rdi
48 0f bf fd
[...]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit
2023-08-07 13:11 ` Eduard Zingerman
2023-08-07 13:48 ` Eduard Zingerman
@ 2023-08-07 14:40 ` Yonghong Song
2023-08-07 14:45 ` Eduard Zingerman
1 sibling, 1 reply; 7+ messages in thread
From: Yonghong Song @ 2023-08-07 14:40 UTC (permalink / raw)
To: Eduard Zingerman, syzbot, andrii, ast, bpf, daniel, davem, haoluo,
hawk, john.fastabend, jolsa, kpsingh, kuba, linux-kernel,
martin.lau, netdev, sdf, song, syzkaller-bugs
On 8/7/23 6:11 AM, Eduard Zingerman wrote:
> On Sun, 2023-08-06 at 23:40 -0700, Yonghong Song wrote:
>>
>> On 8/6/23 4:23 PM, syzbot wrote:
>>> Hello,
>>>
>>> syzbot found the following issue on:
>>>
>>> HEAD commit: 25ad10658dc1 riscv, bpf: Adapt bpf trampoline to optimized..
>>> git tree: bpf-next
>>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=147cbb29a80000
>>> kernel config: https://syzkaller.appspot.com/x/.config?x=8acaeb93ad7c6aaa
>>> dashboard link: https://syzkaller.appspot.com/bug?extid=d61b595e9205573133b3
>>> 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=14d73ccea80000
>>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1276aedea80000
>>>
>>> Downloadable assets:
>>> disk image: https://storage.googleapis.com/syzbot-assets/3d378cc13d42/disk-25ad1065.raw.xz
>>> vmlinux: https://storage.googleapis.com/syzbot-assets/44580fd5d1af/vmlinux-25ad1065.xz
>>> kernel image: https://storage.googleapis.com/syzbot-assets/840587618b41/bzImage-25ad1065.xz
>>>
>>> The issue was bisected to:
>>>
>>> commit 8100928c881482a73ed8bd499d602bab0fe55608
>>> Author: Yonghong Song <yonghong.song@linux.dev>
>>> Date: Fri Jul 28 01:12:02 2023 +0000
>>>
>>> bpf: Support new sign-extension mov insns
>>
>> Thanks for reporting. I will look into this ASAP.
>
> Hi Yonghong,
>
> I guess it's your night and my morning, so I did some initial assessment.
> The BPF program being loaded is:
>
> 0 : (62) *(u32 *)(r10 -8) = 553656332
> 1 : (bf) r1 = (s16)r10
> 2 : (07) r1 += -8
> 3 : (b7) r2 = 3
> 4 : (bd) if r2 <= r1 goto pc+0
> 5 : (85) call bpf_trace_printk#6
> 6 : (b7) r0 = 0
> 7 : (95) exit
>
> (Note: when using bpftool (prog dump xlated id <some-id>) the disassembly
> of the instruction #1 is incorrectly printed as "1: (bf) r1 = r10")
>
> The error occurs when instruction #5 (call to printk) is executed.
> An incorrect address for the format string is passed to printk.
> Disassembly of the jited program looks as follows:
>
> $ bpftool prog dump jited id <some-id>
> bpf_prog_ebeed182d92b487f:
> 0: nopl (%rax,%rax)
> 5: nop
> 7: pushq %rbp
> 8: movq %rsp, %rbp
> b: subq $8, %rsp
> 12: movl $553656332, -8(%rbp)
> 19: movswq %bp, %rdi ; <---- Note movswq %bp !
> 1d: addq $-8, %rdi
> 21: movl $3, %esi
> 26: cmpq %rdi, %rsi
> 29: jbe 0x2b
> 2b: callq 0xffffffffe11c484c
> 30: xorl %eax, %eax
> 32: leave
> 33: retq
>
> Note jit instruction #19 corresponding to BPF instruction #1, which
> loads truncated and sign-extended value of %rbp's first byte as an
> address of format string.
>
> Here is how verifier log looks for (slightly modified) program:
>
> func#0 @0
> 0: R1=ctx(off=0,imm=0) R10=fp0
> ; asm volatile (" \n\
> 0: (b7) r1 = 553656332 ; R1_w=553656332
> 1: (63) *(u32 *)(r10 -8) = r1 ; R1_w=553656332 R10=fp0 fp-8=553656332
> 2: (bf) r1 = (s16)r10 ; R1_w=fp0 R10=fp0
> 3: (07) r1 += -8 ; R1_w=fp-8
> 4: (b7) r2 = 3 ; R2_w=3
> 5: (bd) if r2 <= r1 goto pc+0 ; R1_w=fp-8 R2_w=3
> 6: (85) call bpf_trace_printk#6
> mark_precise: frame0: last_idx 6 first_idx 0 subseq_idx -1
> ...
> mark_precise: frame0: falling back to forcing all scalars precise
> 7: R0=scalar()
> 7: (b7) r0 = 0 ; R0_w=0
> 8: (95) exit
>
> from 5 to 6: R1_w=fp-8 R2_w=3 R10=fp0 fp-8=553656332
> 6: (85) call bpf_trace_printk#6
> mark_precise: frame0: last_idx 6 first_idx 0 subseq_idx -1
> ...
> mark_precise: frame0: falling back to forcing all scalars precise
> 7: safe
>
> Note the following line:
>
> 2: (bf) r1 = (s16)r10 ; R1_w=fp0 R10=fp0
>
> Verifier incorrectly marked r1 as fp0, hence not noticing the problem
> with address passed to printk.
Thanks, Eduard. Right. I am also able to dump xlated code like
below:
0: (62) *(u32 *)(r10 -8) = 553656332
1: (bf) r1 = (s16)r10
2: (07) r1 += -8
3: (b7) r2 = 3
4: (bd) if r2 <= r1 goto pc+0
5: (85) call bpf_trace_printk#-138320
6: (b7) r0 = 0
7: (95) exit
Something like below can fix the problem,
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 132f25dab931..db72619551b2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13171,6 +13171,7 @@ static int check_alu_op(struct bpf_verifier_env
*env, struct bpf_insn *insn)
if (no_sext && need_id)
src_reg->id =
++env->id_gen;
copy_register_state(dst_reg,
src_reg);
+ dst_reg->type = SCALAR_VALUE;
if (!no_sext)
dst_reg->id = 0;
coerce_reg_to_size_sx(dst_reg,
insn->off >> 3);
After insn 1, we need change r1 type to SCALAR_VALUE. Will add
the the test to selftest and submit the patch to fix the problem
today.
>
> Thanks,
> Eduard.
>
>>>
>>> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17970c5da80000
>>> final oops: https://syzkaller.appspot.com/x/report.txt?x=14570c5da80000
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=10570c5da80000
>>>
[...]
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit
2023-08-07 14:40 ` Yonghong Song
@ 2023-08-07 14:45 ` Eduard Zingerman
2023-08-07 18:09 ` Yonghong Song
0 siblings, 1 reply; 7+ messages in thread
From: Eduard Zingerman @ 2023-08-07 14:45 UTC (permalink / raw)
To: yonghong.song, syzbot, andrii, ast, bpf, daniel, davem, haoluo,
hawk, john.fastabend, jolsa, kpsingh, kuba, linux-kernel,
martin.lau, netdev, sdf, song, syzkaller-bugs
On Mon, 2023-08-07 at 07:40 -0700, Yonghong Song wrote:
>
> On 8/7/23 6:11 AM, Eduard Zingerman wrote:
> > On Sun, 2023-08-06 at 23:40 -0700, Yonghong Song wrote:
> > >
> > > On 8/6/23 4:23 PM, syzbot wrote:
> > > > Hello,
> > > >
> > > > syzbot found the following issue on:
> > > >
> > > > HEAD commit: 25ad10658dc1 riscv, bpf: Adapt bpf trampoline to optimized..
> > > > git tree: bpf-next
> > > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=147cbb29a80000
> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=8acaeb93ad7c6aaa
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=d61b595e9205573133b3
> > > > 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=14d73ccea80000
> > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1276aedea80000
> > > >
> > > > Downloadable assets:
> > > > disk image: https://storage.googleapis.com/syzbot-assets/3d378cc13d42/disk-25ad1065.raw.xz
> > > > vmlinux: https://storage.googleapis.com/syzbot-assets/44580fd5d1af/vmlinux-25ad1065.xz
> > > > kernel image: https://storage.googleapis.com/syzbot-assets/840587618b41/bzImage-25ad1065.xz
> > > >
> > > > The issue was bisected to:
> > > >
> > > > commit 8100928c881482a73ed8bd499d602bab0fe55608
> > > > Author: Yonghong Song <yonghong.song@linux.dev>
> > > > Date: Fri Jul 28 01:12:02 2023 +0000
> > > >
> > > > bpf: Support new sign-extension mov insns
> > >
> > > Thanks for reporting. I will look into this ASAP.
> >
> > Hi Yonghong,
> >
> > I guess it's your night and my morning, so I did some initial assessment.
> > The BPF program being loaded is:
> >
> > 0 : (62) *(u32 *)(r10 -8) = 553656332
> > 1 : (bf) r1 = (s16)r10
> > 2 : (07) r1 += -8
> > 3 : (b7) r2 = 3
> > 4 : (bd) if r2 <= r1 goto pc+0
> > 5 : (85) call bpf_trace_printk#6
> > 6 : (b7) r0 = 0
> > 7 : (95) exit
> >
> > (Note: when using bpftool (prog dump xlated id <some-id>) the disassembly
> > of the instruction #1 is incorrectly printed as "1: (bf) r1 = r10")
> >
> > The error occurs when instruction #5 (call to printk) is executed.
> > An incorrect address for the format string is passed to printk.
> > Disassembly of the jited program looks as follows:
> >
> > $ bpftool prog dump jited id <some-id>
> > bpf_prog_ebeed182d92b487f:
> > 0: nopl (%rax,%rax)
> > 5: nop
> > 7: pushq %rbp
> > 8: movq %rsp, %rbp
> > b: subq $8, %rsp
> > 12: movl $553656332, -8(%rbp)
> > 19: movswq %bp, %rdi ; <---- Note movswq %bp !
> > 1d: addq $-8, %rdi
> > 21: movl $3, %esi
> > 26: cmpq %rdi, %rsi
> > 29: jbe 0x2b
> > 2b: callq 0xffffffffe11c484c
> > 30: xorl %eax, %eax
> > 32: leave
> > 33: retq
> >
> > Note jit instruction #19 corresponding to BPF instruction #1, which
> > loads truncated and sign-extended value of %rbp's first byte as an
> > address of format string.
> >
> > Here is how verifier log looks for (slightly modified) program:
> >
> > func#0 @0
> > 0: R1=ctx(off=0,imm=0) R10=fp0
> > ; asm volatile (" \n\
> > 0: (b7) r1 = 553656332 ; R1_w=553656332
> > 1: (63) *(u32 *)(r10 -8) = r1 ; R1_w=553656332 R10=fp0 fp-8=553656332
> > 2: (bf) r1 = (s16)r10 ; R1_w=fp0 R10=fp0
> > 3: (07) r1 += -8 ; R1_w=fp-8
> > 4: (b7) r2 = 3 ; R2_w=3
> > 5: (bd) if r2 <= r1 goto pc+0 ; R1_w=fp-8 R2_w=3
> > 6: (85) call bpf_trace_printk#6
> > mark_precise: frame0: last_idx 6 first_idx 0 subseq_idx -1
> > ...
> > mark_precise: frame0: falling back to forcing all scalars precise
> > 7: R0=scalar()
> > 7: (b7) r0 = 0 ; R0_w=0
> > 8: (95) exit
> >
> > from 5 to 6: R1_w=fp-8 R2_w=3 R10=fp0 fp-8=553656332
> > 6: (85) call bpf_trace_printk#6
> > mark_precise: frame0: last_idx 6 first_idx 0 subseq_idx -1
> > ...
> > mark_precise: frame0: falling back to forcing all scalars precise
> > 7: safe
> >
> > Note the following line:
> >
> > 2: (bf) r1 = (s16)r10 ; R1_w=fp0 R10=fp0
> >
> > Verifier incorrectly marked r1 as fp0, hence not noticing the problem
> > with address passed to printk.
>
> Thanks, Eduard. Right. I am also able to dump xlated code like
> below:
>
> 0: (62) *(u32 *)(r10 -8) = 553656332
> 1: (bf) r1 = (s16)r10
> 2: (07) r1 += -8
> 3: (b7) r2 = 3
> 4: (bd) if r2 <= r1 goto pc+0
> 5: (85) call bpf_trace_printk#-138320
> 6: (b7) r0 = 0
> 7: (95) exit
>
> Something like below can fix the problem,
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 132f25dab931..db72619551b2 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -13171,6 +13171,7 @@ static int check_alu_op(struct bpf_verifier_env
> *env, struct bpf_insn *insn)
> if (no_sext && need_id)
> src_reg->id =
> ++env->id_gen;
> copy_register_state(dst_reg,
> src_reg);
> + dst_reg->type = SCALAR_VALUE;
> if (!no_sext)
> dst_reg->id = 0;
> coerce_reg_to_size_sx(dst_reg,
> insn->off >> 3);
>
> After insn 1, we need change r1 type to SCALAR_VALUE. Will add
> the the test to selftest and submit the patch to fix the problem
> today.
Should this be an error?
Like in the same function but slightly below, when u32 moves are
processed:
/* R1 = (u32) R2 */
if (is_pointer_value(env, insn->src_reg)) {
verbose(env,
"R%d partial copy of pointer\n",
insn->src_reg);
return -EACCES;
} else { ...
>
> >
> > Thanks,
> > Eduard.
> >
> > > >
> > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17970c5da80000
> > > > final oops: https://syzkaller.appspot.com/x/report.txt?x=14570c5da80000
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=10570c5da80000
> > > >
> [...]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit
2023-08-07 14:45 ` Eduard Zingerman
@ 2023-08-07 18:09 ` Yonghong Song
0 siblings, 0 replies; 7+ messages in thread
From: Yonghong Song @ 2023-08-07 18:09 UTC (permalink / raw)
To: Eduard Zingerman, syzbot, andrii, ast, bpf, daniel, davem, haoluo,
hawk, john.fastabend, jolsa, kpsingh, kuba, linux-kernel,
martin.lau, netdev, sdf, song, syzkaller-bugs
On 8/7/23 7:45 AM, Eduard Zingerman wrote:
> On Mon, 2023-08-07 at 07:40 -0700, Yonghong Song wrote:
>>
>> On 8/7/23 6:11 AM, Eduard Zingerman wrote:
>>> On Sun, 2023-08-06 at 23:40 -0700, Yonghong Song wrote:
>>>>
>>>> On 8/6/23 4:23 PM, syzbot wrote:
>>>>> Hello,
>>>>>
>>>>> syzbot found the following issue on:
>>>>>
>>>>> HEAD commit: 25ad10658dc1 riscv, bpf: Adapt bpf trampoline to optimized..
>>>>> git tree: bpf-next
>>>>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=147cbb29a80000
>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=8acaeb93ad7c6aaa
>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=d61b595e9205573133b3
>>>>> 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=14d73ccea80000
>>>>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1276aedea80000
>>>>>
>>>>> Downloadable assets:
>>>>> disk image: https://storage.googleapis.com/syzbot-assets/3d378cc13d42/disk-25ad1065.raw.xz
>>>>> vmlinux: https://storage.googleapis.com/syzbot-assets/44580fd5d1af/vmlinux-25ad1065.xz
>>>>> kernel image: https://storage.googleapis.com/syzbot-assets/840587618b41/bzImage-25ad1065.xz
>>>>>
>>>>> The issue was bisected to:
>>>>>
>>>>> commit 8100928c881482a73ed8bd499d602bab0fe55608
>>>>> Author: Yonghong Song <yonghong.song@linux.dev>
>>>>> Date: Fri Jul 28 01:12:02 2023 +0000
>>>>>
>>>>> bpf: Support new sign-extension mov insns
>>>>
>>>> Thanks for reporting. I will look into this ASAP.
>>>
>>> Hi Yonghong,
>>>
>>> I guess it's your night and my morning, so I did some initial assessment.
>>> The BPF program being loaded is:
>>>
>>> 0 : (62) *(u32 *)(r10 -8) = 553656332
>>> 1 : (bf) r1 = (s16)r10
>>> 2 : (07) r1 += -8
>>> 3 : (b7) r2 = 3
>>> 4 : (bd) if r2 <= r1 goto pc+0
>>> 5 : (85) call bpf_trace_printk#6
>>> 6 : (b7) r0 = 0
>>> 7 : (95) exit
>>>
>>> (Note: when using bpftool (prog dump xlated id <some-id>) the disassembly
>>> of the instruction #1 is incorrectly printed as "1: (bf) r1 = r10")
>>>
>>> The error occurs when instruction #5 (call to printk) is executed.
>>> An incorrect address for the format string is passed to printk.
>>> Disassembly of the jited program looks as follows:
>>>
>>> $ bpftool prog dump jited id <some-id>
>>> bpf_prog_ebeed182d92b487f:
>>> 0: nopl (%rax,%rax)
>>> 5: nop
>>> 7: pushq %rbp
>>> 8: movq %rsp, %rbp
>>> b: subq $8, %rsp
>>> 12: movl $553656332, -8(%rbp)
>>> 19: movswq %bp, %rdi ; <---- Note movswq %bp !
>>> 1d: addq $-8, %rdi
>>> 21: movl $3, %esi
>>> 26: cmpq %rdi, %rsi
>>> 29: jbe 0x2b
>>> 2b: callq 0xffffffffe11c484c
>>> 30: xorl %eax, %eax
>>> 32: leave
>>> 33: retq
>>>
>>> Note jit instruction #19 corresponding to BPF instruction #1, which
>>> loads truncated and sign-extended value of %rbp's first byte as an
>>> address of format string.
>>>
>>> Here is how verifier log looks for (slightly modified) program:
>>>
>>> func#0 @0
>>> 0: R1=ctx(off=0,imm=0) R10=fp0
>>> ; asm volatile (" \n\
>>> 0: (b7) r1 = 553656332 ; R1_w=553656332
>>> 1: (63) *(u32 *)(r10 -8) = r1 ; R1_w=553656332 R10=fp0 fp-8=553656332
>>> 2: (bf) r1 = (s16)r10 ; R1_w=fp0 R10=fp0
>>> 3: (07) r1 += -8 ; R1_w=fp-8
>>> 4: (b7) r2 = 3 ; R2_w=3
>>> 5: (bd) if r2 <= r1 goto pc+0 ; R1_w=fp-8 R2_w=3
>>> 6: (85) call bpf_trace_printk#6
>>> mark_precise: frame0: last_idx 6 first_idx 0 subseq_idx -1
>>> ...
>>> mark_precise: frame0: falling back to forcing all scalars precise
>>> 7: R0=scalar()
>>> 7: (b7) r0 = 0 ; R0_w=0
>>> 8: (95) exit
>>>
>>> from 5 to 6: R1_w=fp-8 R2_w=3 R10=fp0 fp-8=553656332
>>> 6: (85) call bpf_trace_printk#6
>>> mark_precise: frame0: last_idx 6 first_idx 0 subseq_idx -1
>>> ...
>>> mark_precise: frame0: falling back to forcing all scalars precise
>>> 7: safe
>>>
>>> Note the following line:
>>>
>>> 2: (bf) r1 = (s16)r10 ; R1_w=fp0 R10=fp0
>>>
>>> Verifier incorrectly marked r1 as fp0, hence not noticing the problem
>>> with address passed to printk.
>>
>> Thanks, Eduard. Right. I am also able to dump xlated code like
>> below:
>>
>> 0: (62) *(u32 *)(r10 -8) = 553656332
>> 1: (bf) r1 = (s16)r10
>> 2: (07) r1 += -8
>> 3: (b7) r2 = 3
>> 4: (bd) if r2 <= r1 goto pc+0
>> 5: (85) call bpf_trace_printk#-138320
>> 6: (b7) r0 = 0
>> 7: (95) exit
>>
>> Something like below can fix the problem,
>>
>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>> index 132f25dab931..db72619551b2 100644
>> --- a/kernel/bpf/verifier.c
>> +++ b/kernel/bpf/verifier.c
>> @@ -13171,6 +13171,7 @@ static int check_alu_op(struct bpf_verifier_env
>> *env, struct bpf_insn *insn)
>> if (no_sext && need_id)
>> src_reg->id =
>> ++env->id_gen;
>> copy_register_state(dst_reg,
>> src_reg);
>> + dst_reg->type = SCALAR_VALUE;
>> if (!no_sext)
>> dst_reg->id = 0;
>> coerce_reg_to_size_sx(dst_reg,
>> insn->off >> 3);
>>
>> After insn 1, we need change r1 type to SCALAR_VALUE. Will add
>> the the test to selftest and submit the patch to fix the problem
>> today.
>
> Should this be an error?
> Like in the same function but slightly below, when u32 moves are
> processed:
>
> /* R1 = (u32) R2 */
> if (is_pointer_value(env, insn->src_reg)) {
> verbose(env,
> "R%d partial copy of pointer\n",
> insn->src_reg);
> return -EACCES;
> } else { ...
Right, this is indeed better for unprivileged prog run.
I have submitted a patch to fix the issue reported by syzbot.
Please help review. Thanks!
>
>>
>>>
>>> Thanks,
>>> Eduard.
>>>
>>>>>
>>>>> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17970c5da80000
>>>>> final oops: https://syzkaller.appspot.com/x/report.txt?x=14570c5da80000
>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=10570c5da80000
>>>>>
>> [...]
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2023-08-07 18:09 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-08-06 23:23 [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit syzbot
2023-08-07 6:40 ` Yonghong Song
2023-08-07 13:11 ` Eduard Zingerman
2023-08-07 13:48 ` Eduard Zingerman
2023-08-07 14:40 ` Yonghong Song
2023-08-07 14:45 ` Eduard Zingerman
2023-08-07 18:09 ` Yonghong Song
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