[syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start

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* [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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