* [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve
@ 2022-08-11 7:29 syzbot
2022-08-11 15:33 ` Kees Cook
0 siblings, 1 reply; 8+ messages in thread
From: syzbot @ 2022-08-11 7:29 UTC (permalink / raw)
To: ebiederm, keescook, linux-fsdevel, linux-kernel, linux-mm,
linux-next, sfr, syzkaller-bugs, viro
Hello,
syzbot found the following issue on:
HEAD commit: bc6c6584ffb2 Add linux-next specific files for 20220810
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=115034c3080000
kernel config: https://syzkaller.appspot.com/x/.config?x=5784be4315a4403b
dashboard link: https://syzkaller.appspot.com/bug?extid=3250d9c8925ef29e975f
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3250d9c8925ef29e975f@syzkaller.appspotmail.com
BUG: unable to handle page fault for address: ffffdc0000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 11826067 P4D 11826067 PUD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 1100 Comm: kworker/u4:5 Not tainted 5.19.0-next-20220810-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
strnlen include/linux/fortify-string.h:119 [inline]
copy_string_kernel+0x26/0x250 fs/exec.c:616
copy_strings_kernel+0xb3/0x190 fs/exec.c:655
kernel_execve+0x377/0x500 fs/exec.c:1998
call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>
Modules linked in:
CR2: ffffdc0000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 74 3c je 0x3e
2: 48 bb 00 00 00 00 00 movabs $0xdffffc0000000000,%rbx
9: fc ff df
c: 49 89 fc mov %rdi,%r12
f: 48 89 f8 mov %rdi,%rax
12: eb 09 jmp 0x1d
14: 48 83 c0 01 add $0x1,%rax
18: 48 39 e8 cmp %rbp,%rax
1b: 74 1e je 0x3b
1d: 48 89 c2 mov %rax,%rdx
20: 48 89 c1 mov %rax,%rcx
23: 48 c1 ea 03 shr $0x3,%rdx
27: 83 e1 07 and $0x7,%ecx
* 2a: 0f b6 14 1a movzbl (%rdx,%rbx,1),%edx <-- trapping instruction
2e: 38 ca cmp %cl,%dl
30: 7f 04 jg 0x36
32: 84 d2 test %dl,%dl
34: 75 11 jne 0x47
36: 80 38 00 cmpb $0x0,(%rax)
39: 75 d9 jne 0x14
3b: 4c 29 e0 sub %r12,%rax
3e: 48 rex.W
3f: 83 .byte 0x83
---
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.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve
2022-08-11 7:29 [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve syzbot
@ 2022-08-11 15:33 ` Kees Cook
2022-08-11 17:39 ` Ira Weiny
0 siblings, 1 reply; 8+ messages in thread
From: Kees Cook @ 2022-08-11 15:33 UTC (permalink / raw)
To: Fabio M. De Francesco
Cc: ebiederm, linux-fsdevel, linux-kernel, linux-mm, linux-next, sfr,
syzkaller-bugs, viro, syzbot, Ira Weiny
Hi Fabio,
It seems likely that the kmap change[1] might be causing this crash. Is
there a boot-time setup race between kmap being available and early umh
usage?
-Kees
[1] https://git.kernel.org/linus/c6e8e36c6ae4b11bed5643317afb66b6c3cadba8
On Thu, Aug 11, 2022 at 12:29:34AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: bc6c6584ffb2 Add linux-next specific files for 20220810
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=115034c3080000
> kernel config: https://syzkaller.appspot.com/x/.config?x=5784be4315a4403b
> dashboard link: https://syzkaller.appspot.com/bug?extid=3250d9c8925ef29e975f
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3250d9c8925ef29e975f@syzkaller.appspotmail.com
>
> BUG: unable to handle page fault for address: ffffdc0000000000
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 11826067 P4D 11826067 PUD 0
> Oops: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 1100 Comm: kworker/u4:5 Not tainted 5.19.0-next-20220810-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
> RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> strnlen include/linux/fortify-string.h:119 [inline]
> copy_string_kernel+0x26/0x250 fs/exec.c:616
> copy_strings_kernel+0xb3/0x190 fs/exec.c:655
> kernel_execve+0x377/0x500 fs/exec.c:1998
> call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
> </TASK>
> Modules linked in:
> CR2: ffffdc0000000000
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
> 0: 74 3c je 0x3e
> 2: 48 bb 00 00 00 00 00 movabs $0xdffffc0000000000,%rbx
> 9: fc ff df
> c: 49 89 fc mov %rdi,%r12
> f: 48 89 f8 mov %rdi,%rax
> 12: eb 09 jmp 0x1d
> 14: 48 83 c0 01 add $0x1,%rax
> 18: 48 39 e8 cmp %rbp,%rax
> 1b: 74 1e je 0x3b
> 1d: 48 89 c2 mov %rax,%rdx
> 20: 48 89 c1 mov %rax,%rcx
> 23: 48 c1 ea 03 shr $0x3,%rdx
> 27: 83 e1 07 and $0x7,%ecx
> * 2a: 0f b6 14 1a movzbl (%rdx,%rbx,1),%edx <-- trapping instruction
> 2e: 38 ca cmp %cl,%dl
> 30: 7f 04 jg 0x36
> 32: 84 d2 test %dl,%dl
> 34: 75 11 jne 0x47
> 36: 80 38 00 cmpb $0x0,(%rax)
> 39: 75 d9 jne 0x14
> 3b: 4c 29 e0 sub %r12,%rax
> 3e: 48 rex.W
> 3f: 83 .byte 0x83
>
>
> ---
> 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.
--
Kees Cook
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve
2022-08-11 15:33 ` Kees Cook
@ 2022-08-11 17:39 ` Ira Weiny
2022-08-11 18:51 ` Ira Weiny
0 siblings, 1 reply; 8+ messages in thread
From: Ira Weiny @ 2022-08-11 17:39 UTC (permalink / raw)
To: Kees Cook
Cc: Fabio M. De Francesco, ebiederm, linux-fsdevel, linux-kernel,
linux-mm, linux-next, sfr, syzkaller-bugs, viro, syzbot
On Thu, Aug 11, 2022 at 08:33:16AM -0700, Kees Cook wrote:
> Hi Fabio,
>
> It seems likely that the kmap change[1] might be causing this crash. Is
> there a boot-time setup race between kmap being available and early umh
> usage?
I don't see how this is a setup problem with the config reported here.
CONFIG_64BIT=y
...and HIGHMEM is not set.
...and PREEMPT_RT is not set.
So the kmap_local_page() call in that stack should be a page_address() only.
I think the issue must be some sort of race which was being prevented because
of the preemption and/or pagefault disable built into kmap_atomic().
Is this reproducable?
The hunk below will surely fix it but I think the pagefault_disable() is
the only thing that is required. It would be nice to test it.
Ira
diff --git a/fs/exec.c b/fs/exec.c
index b51dd14e7388..3da588c858ca 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -640,7 +640,11 @@ int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
if (!page)
return -E2BIG;
flush_arg_page(bprm, pos & PAGE_MASK, page);
+ preempt_disable();
+ pagefault_disable();
memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
+ pagefault_enable();
+ preempt_enable();
put_arg_page(page);
}
>
> -Kees
>
> [1] https://git.kernel.org/linus/c6e8e36c6ae4b11bed5643317afb66b6c3cadba8
>
> On Thu, Aug 11, 2022 at 12:29:34AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: bc6c6584ffb2 Add linux-next specific files for 20220810
> > git tree: linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=115034c3080000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=5784be4315a4403b
> > dashboard link: https://syzkaller.appspot.com/bug?extid=3250d9c8925ef29e975f
> > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+3250d9c8925ef29e975f@syzkaller.appspotmail.com
> >
> > BUG: unable to handle page fault for address: ffffdc0000000000
> > #PF: supervisor read access in kernel mode
> > #PF: error_code(0x0000) - not-present page
> > PGD 11826067 P4D 11826067 PUD 0
> > Oops: 0000 [#1] PREEMPT SMP KASAN
> > CPU: 0 PID: 1100 Comm: kworker/u4:5 Not tainted 5.19.0-next-20220810-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
> > RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> > Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> > RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> > RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> > RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> > R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> > R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> > FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> > <TASK>
> > strnlen include/linux/fortify-string.h:119 [inline]
> > copy_string_kernel+0x26/0x250 fs/exec.c:616
> > copy_strings_kernel+0xb3/0x190 fs/exec.c:655
> > kernel_execve+0x377/0x500 fs/exec.c:1998
> > call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
> > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
> > </TASK>
> > Modules linked in:
> > CR2: ffffdc0000000000
> > ---[ end trace 0000000000000000 ]---
> > RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> > Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> > RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> > RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> > RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> > R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> > R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> > FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > ----------------
> > Code disassembly (best guess):
> > 0: 74 3c je 0x3e
> > 2: 48 bb 00 00 00 00 00 movabs $0xdffffc0000000000,%rbx
> > 9: fc ff df
> > c: 49 89 fc mov %rdi,%r12
> > f: 48 89 f8 mov %rdi,%rax
> > 12: eb 09 jmp 0x1d
> > 14: 48 83 c0 01 add $0x1,%rax
> > 18: 48 39 e8 cmp %rbp,%rax
> > 1b: 74 1e je 0x3b
> > 1d: 48 89 c2 mov %rax,%rdx
> > 20: 48 89 c1 mov %rax,%rcx
> > 23: 48 c1 ea 03 shr $0x3,%rdx
> > 27: 83 e1 07 and $0x7,%ecx
> > * 2a: 0f b6 14 1a movzbl (%rdx,%rbx,1),%edx <-- trapping instruction
> > 2e: 38 ca cmp %cl,%dl
> > 30: 7f 04 jg 0x36
> > 32: 84 d2 test %dl,%dl
> > 34: 75 11 jne 0x47
> > 36: 80 38 00 cmpb $0x0,(%rax)
> > 39: 75 d9 jne 0x14
> > 3b: 4c 29 e0 sub %r12,%rax
> > 3e: 48 rex.W
> > 3f: 83 .byte 0x83
> >
> >
> > ---
> > 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.
>
> --
> Kees Cook
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve
2022-08-11 17:39 ` Ira Weiny
@ 2022-08-11 18:51 ` Ira Weiny
2022-08-11 21:00 ` Kees Cook
0 siblings, 1 reply; 8+ messages in thread
From: Ira Weiny @ 2022-08-11 18:51 UTC (permalink / raw)
To: Kees Cook
Cc: Fabio M. De Francesco, ebiederm, linux-fsdevel, linux-kernel,
linux-mm, linux-next, sfr, syzkaller-bugs, viro, syzbot
On Thu, Aug 11, 2022 at 10:39:29AM -0700, Ira wrote:
> On Thu, Aug 11, 2022 at 08:33:16AM -0700, Kees Cook wrote:
> > Hi Fabio,
> >
> > It seems likely that the kmap change[1] might be causing this crash. Is
> > there a boot-time setup race between kmap being available and early umh
> > usage?
>
> I don't see how this is a setup problem with the config reported here.
>
> CONFIG_64BIT=y
>
> ...and HIGHMEM is not set.
> ...and PREEMPT_RT is not set.
>
> So the kmap_local_page() call in that stack should be a page_address() only.
>
> I think the issue must be some sort of race which was being prevented because
> of the preemption and/or pagefault disable built into kmap_atomic().
>
> Is this reproducable?
>
> The hunk below will surely fix it but I think the pagefault_disable() is
> the only thing that is required. It would be nice to test it.
Fabio and I discussed this. And he also mentioned that pagefault_disable() is
all that is required.
Do we have a way to test this?
Ira
>
> Ira
>
>
> diff --git a/fs/exec.c b/fs/exec.c
> index b51dd14e7388..3da588c858ca 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -640,7 +640,11 @@ int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
> if (!page)
> return -E2BIG;
> flush_arg_page(bprm, pos & PAGE_MASK, page);
> + preempt_disable();
> + pagefault_disable();
> memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
> + pagefault_enable();
> + preempt_enable();
> put_arg_page(page);
> }
>
>
> >
> > -Kees
> >
> > [1] https://git.kernel.org/linus/c6e8e36c6ae4b11bed5643317afb66b6c3cadba8
> >
> > On Thu, Aug 11, 2022 at 12:29:34AM -0700, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: bc6c6584ffb2 Add linux-next specific files for 20220810
> > > git tree: linux-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=115034c3080000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=5784be4315a4403b
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=3250d9c8925ef29e975f
> > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+3250d9c8925ef29e975f@syzkaller.appspotmail.com
> > >
> > > BUG: unable to handle page fault for address: ffffdc0000000000
> > > #PF: supervisor read access in kernel mode
> > > #PF: error_code(0x0000) - not-present page
> > > PGD 11826067 P4D 11826067 PUD 0
> > > Oops: 0000 [#1] PREEMPT SMP KASAN
> > > CPU: 0 PID: 1100 Comm: kworker/u4:5 Not tainted 5.19.0-next-20220810-syzkaller #0
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
> > > RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> > > Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> > > RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> > > RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > > RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> > > RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> > > R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> > > R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> > > FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > Call Trace:
> > > <TASK>
> > > strnlen include/linux/fortify-string.h:119 [inline]
> > > copy_string_kernel+0x26/0x250 fs/exec.c:616
> > > copy_strings_kernel+0xb3/0x190 fs/exec.c:655
> > > kernel_execve+0x377/0x500 fs/exec.c:1998
> > > call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
> > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
> > > </TASK>
> > > Modules linked in:
> > > CR2: ffffdc0000000000
> > > ---[ end trace 0000000000000000 ]---
> > > RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> > > Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> > > RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> > > RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > > RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> > > RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> > > R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> > > R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> > > FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > ----------------
> > > Code disassembly (best guess):
> > > 0: 74 3c je 0x3e
> > > 2: 48 bb 00 00 00 00 00 movabs $0xdffffc0000000000,%rbx
> > > 9: fc ff df
> > > c: 49 89 fc mov %rdi,%r12
> > > f: 48 89 f8 mov %rdi,%rax
> > > 12: eb 09 jmp 0x1d
> > > 14: 48 83 c0 01 add $0x1,%rax
> > > 18: 48 39 e8 cmp %rbp,%rax
> > > 1b: 74 1e je 0x3b
> > > 1d: 48 89 c2 mov %rax,%rdx
> > > 20: 48 89 c1 mov %rax,%rcx
> > > 23: 48 c1 ea 03 shr $0x3,%rdx
> > > 27: 83 e1 07 and $0x7,%ecx
> > > * 2a: 0f b6 14 1a movzbl (%rdx,%rbx,1),%edx <-- trapping instruction
> > > 2e: 38 ca cmp %cl,%dl
> > > 30: 7f 04 jg 0x36
> > > 32: 84 d2 test %dl,%dl
> > > 34: 75 11 jne 0x47
> > > 36: 80 38 00 cmpb $0x0,(%rax)
> > > 39: 75 d9 jne 0x14
> > > 3b: 4c 29 e0 sub %r12,%rax
> > > 3e: 48 rex.W
> > > 3f: 83 .byte 0x83
> > >
> > >
> > > ---
> > > 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.
> >
> > --
> > Kees Cook
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve
2022-08-11 18:51 ` Ira Weiny
@ 2022-08-11 21:00 ` Kees Cook
2022-08-12 0:11 ` Ira Weiny
0 siblings, 1 reply; 8+ messages in thread
From: Kees Cook @ 2022-08-11 21:00 UTC (permalink / raw)
To: Ira Weiny
Cc: Fabio M. De Francesco, ebiederm, linux-fsdevel, linux-kernel,
linux-mm, linux-next, sfr, syzkaller-bugs, viro, syzbot
On Thu, Aug 11, 2022 at 11:51:34AM -0700, Ira Weiny wrote:
> On Thu, Aug 11, 2022 at 10:39:29AM -0700, Ira wrote:
> > On Thu, Aug 11, 2022 at 08:33:16AM -0700, Kees Cook wrote:
> > > Hi Fabio,
> > >
> > > It seems likely that the kmap change[1] might be causing this crash. Is
> > > there a boot-time setup race between kmap being available and early umh
> > > usage?
> >
> > I don't see how this is a setup problem with the config reported here.
> >
> > CONFIG_64BIT=y
> >
> > ...and HIGHMEM is not set.
> > ...and PREEMPT_RT is not set.
> >
> > So the kmap_local_page() call in that stack should be a page_address() only.
> >
> > I think the issue must be some sort of race which was being prevented because
> > of the preemption and/or pagefault disable built into kmap_atomic().
> >
> > Is this reproducable?
> >
> > The hunk below will surely fix it but I think the pagefault_disable() is
> > the only thing that is required. It would be nice to test it.
>
> Fabio and I discussed this. And he also mentioned that pagefault_disable() is
> all that is required.
Okay, sounds good.
> Do we have a way to test this?
It doesn't look like syzbot has a reproducer yet, so its patch testing
system[1] will not work. But if you can send me a patch, I could land it
in -next and we could see if the reproduction frequency drops to zero.
(Looking at the dashboard, it's seen 2 crashes, most recently 8 hours
ago.)
-Kees
[1] https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches
> > > > syzbot found the following issue on:
> > > >
> > > > HEAD commit: bc6c6584ffb2 Add linux-next specific files for 20220810
> > > > git tree: linux-next
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=115034c3080000
> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=5784be4315a4403b
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=3250d9c8925ef29e975f
> > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > >
> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > Reported-by: syzbot+3250d9c8925ef29e975f@syzkaller.appspotmail.com
> > > >
> > > > BUG: unable to handle page fault for address: ffffdc0000000000
> > > > #PF: supervisor read access in kernel mode
> > > > #PF: error_code(0x0000) - not-present page
> > > > PGD 11826067 P4D 11826067 PUD 0
> > > > Oops: 0000 [#1] PREEMPT SMP KASAN
> > > > CPU: 0 PID: 1100 Comm: kworker/u4:5 Not tainted 5.19.0-next-20220810-syzkaller #0
> > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
> > > > RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> > > > Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> > > > RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> > > > RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > > > RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> > > > RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> > > > R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> > > > R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> > > > FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > > Call Trace:
> > > > <TASK>
> > > > strnlen include/linux/fortify-string.h:119 [inline]
> > > > copy_string_kernel+0x26/0x250 fs/exec.c:616
> > > > copy_strings_kernel+0xb3/0x190 fs/exec.c:655
> > > > kernel_execve+0x377/0x500 fs/exec.c:1998
> > > > call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
> > > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
> > > > </TASK>
> [...]
> > > > ---
> > > > 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.
--
Kees Cook
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve
2022-08-11 21:00 ` Kees Cook
@ 2022-08-12 0:11 ` Ira Weiny
2022-08-12 9:29 ` Dmitry Vyukov
0 siblings, 1 reply; 8+ messages in thread
From: Ira Weiny @ 2022-08-12 0:11 UTC (permalink / raw)
To: Kees Cook
Cc: Fabio M. De Francesco, ebiederm, linux-fsdevel, linux-kernel,
linux-mm, linux-next, sfr, syzkaller-bugs, viro, syzbot
On Thu, Aug 11, 2022 at 02:00:59PM -0700, Kees Cook wrote:
> On Thu, Aug 11, 2022 at 11:51:34AM -0700, Ira Weiny wrote:
> > On Thu, Aug 11, 2022 at 10:39:29AM -0700, Ira wrote:
> > > On Thu, Aug 11, 2022 at 08:33:16AM -0700, Kees Cook wrote:
> > > > Hi Fabio,
> > > >
> > > > It seems likely that the kmap change[1] might be causing this crash. Is
> > > > there a boot-time setup race between kmap being available and early umh
> > > > usage?
> > >
> > > I don't see how this is a setup problem with the config reported here.
> > >
> > > CONFIG_64BIT=y
> > >
> > > ...and HIGHMEM is not set.
> > > ...and PREEMPT_RT is not set.
> > >
> > > So the kmap_local_page() call in that stack should be a page_address() only.
> > >
> > > I think the issue must be some sort of race which was being prevented because
> > > of the preemption and/or pagefault disable built into kmap_atomic().
> > >
> > > Is this reproducable?
> > >
> > > The hunk below will surely fix it but I think the pagefault_disable() is
> > > the only thing that is required. It would be nice to test it.
> >
> > Fabio and I discussed this. And he also mentioned that pagefault_disable() is
> > all that is required.
>
> Okay, sounds good.
>
> > Do we have a way to test this?
>
> It doesn't look like syzbot has a reproducer yet, so its patch testing
> system[1] will not work. But if you can send me a patch, I could land it
> in -next and we could see if the reproduction frequency drops to zero.
> (Looking at the dashboard, it's seen 2 crashes, most recently 8 hours
> ago.)
Patch sent.
https://lore.kernel.org/lkml/20220812000919.408614-1-ira.weiny@intel.com/
But I'm more confused after looking at this again.
Ira
>
> -Kees
>
> [1] https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches
>
> > > > > syzbot found the following issue on:
> > > > >
> > > > > HEAD commit: bc6c6584ffb2 Add linux-next specific files for 20220810
> > > > > git tree: linux-next
> > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=115034c3080000
> > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=5784be4315a4403b
> > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=3250d9c8925ef29e975f
> > > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > > >
> > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > > Reported-by: syzbot+3250d9c8925ef29e975f@syzkaller.appspotmail.com
> > > > >
> > > > > BUG: unable to handle page fault for address: ffffdc0000000000
> > > > > #PF: supervisor read access in kernel mode
> > > > > #PF: error_code(0x0000) - not-present page
> > > > > PGD 11826067 P4D 11826067 PUD 0
> > > > > Oops: 0000 [#1] PREEMPT SMP KASAN
> > > > > CPU: 0 PID: 1100 Comm: kworker/u4:5 Not tainted 5.19.0-next-20220810-syzkaller #0
> > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
> > > > > RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> > > > > Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> > > > > RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> > > > > RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > > > > RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> > > > > RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> > > > > R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> > > > > R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> > > > > FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> > > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> > > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > > > Call Trace:
> > > > > <TASK>
> > > > > strnlen include/linux/fortify-string.h:119 [inline]
> > > > > copy_string_kernel+0x26/0x250 fs/exec.c:616
> > > > > copy_strings_kernel+0xb3/0x190 fs/exec.c:655
> > > > > kernel_execve+0x377/0x500 fs/exec.c:1998
> > > > > call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
> > > > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
> > > > > </TASK>
> > [...]
> > > > > ---
> > > > > 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.
>
> --
> Kees Cook
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve
2022-08-12 0:11 ` Ira Weiny
@ 2022-08-12 9:29 ` Dmitry Vyukov
2022-08-12 18:44 ` Kees Cook
0 siblings, 1 reply; 8+ messages in thread
From: Dmitry Vyukov @ 2022-08-12 9:29 UTC (permalink / raw)
To: Ira Weiny
Cc: Kees Cook, Fabio M. De Francesco, ebiederm, linux-fsdevel,
linux-kernel, linux-mm, linux-next, sfr, syzkaller-bugs, viro,
syzbot
On Fri, 12 Aug 2022 at 02:11, Ira Weiny <ira.weiny@intel.com> wrote:
>
> On Thu, Aug 11, 2022 at 02:00:59PM -0700, Kees Cook wrote:
> > On Thu, Aug 11, 2022 at 11:51:34AM -0700, Ira Weiny wrote:
> > > On Thu, Aug 11, 2022 at 10:39:29AM -0700, Ira wrote:
> > > > On Thu, Aug 11, 2022 at 08:33:16AM -0700, Kees Cook wrote:
> > > > > Hi Fabio,
> > > > >
> > > > > It seems likely that the kmap change[1] might be causing this crash. Is
> > > > > there a boot-time setup race between kmap being available and early umh
> > > > > usage?
> > > >
> > > > I don't see how this is a setup problem with the config reported here.
> > > >
> > > > CONFIG_64BIT=y
> > > >
> > > > ...and HIGHMEM is not set.
> > > > ...and PREEMPT_RT is not set.
> > > >
> > > > So the kmap_local_page() call in that stack should be a page_address() only.
> > > >
> > > > I think the issue must be some sort of race which was being prevented because
> > > > of the preemption and/or pagefault disable built into kmap_atomic().
> > > >
> > > > Is this reproducable?
> > > >
> > > > The hunk below will surely fix it but I think the pagefault_disable() is
> > > > the only thing that is required. It would be nice to test it.
> > >
> > > Fabio and I discussed this. And he also mentioned that pagefault_disable() is
> > > all that is required.
> >
> > Okay, sounds good.
> >
> > > Do we have a way to test this?
> >
> > It doesn't look like syzbot has a reproducer yet, so its patch testing
> > system[1] will not work. But if you can send me a patch, I could land it
> > in -next and we could see if the reproduction frequency drops to zero.
> > (Looking at the dashboard, it's seen 2 crashes, most recently 8 hours
> > ago.)
>
> Patch sent.
>
> https://lore.kernel.org/lkml/20220812000919.408614-1-ira.weiny@intel.com/
>
> But I'm more confused after looking at this again.
There is splat of random crashes in linux-next happened at the same time:
https://groups.google.com/g/syzkaller-bugs/search?q=%22linux-next%20boot%20error%3A%22
There are 10 different crashes in completely random places.
I would assume they have the same root cause, some silent memory
corruption or something similar.
> > [1] https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches
> >
> > > > > > syzbot found the following issue on:
> > > > > >
> > > > > > HEAD commit: bc6c6584ffb2 Add linux-next specific files for 20220810
> > > > > > git tree: linux-next
> > > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=115034c3080000
> > > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=5784be4315a4403b
> > > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=3250d9c8925ef29e975f
> > > > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > > > >
> > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > > > Reported-by: syzbot+3250d9c8925ef29e975f@syzkaller.appspotmail.com
> > > > > >
> > > > > > BUG: unable to handle page fault for address: ffffdc0000000000
> > > > > > #PF: supervisor read access in kernel mode
> > > > > > #PF: error_code(0x0000) - not-present page
> > > > > > PGD 11826067 P4D 11826067 PUD 0
> > > > > > Oops: 0000 [#1] PREEMPT SMP KASAN
> > > > > > CPU: 0 PID: 1100 Comm: kworker/u4:5 Not tainted 5.19.0-next-20220810-syzkaller #0
> > > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
> > > > > > RIP: 0010:strnlen+0x3b/0x70 lib/string.c:504
> > > > > > Code: 74 3c 48 bb 00 00 00 00 00 fc ff df 49 89 fc 48 89 f8 eb 09 48 83 c0 01 48 39 e8 74 1e 48 89 c2 48 89 c1 48 c1 ea 03 83 e1 07 <0f> b6 14 1a 38 ca 7f 04 84 d2 75 11 80 38 00 75 d9 4c 29 e0 48 83
> > > > > > RSP: 0000:ffffc90005c5fe10 EFLAGS: 00010246
> > > > > > RAX: ffff000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > > > > > RDX: 1fffe00000000000 RSI: 0000000000020000 RDI: ffff000000000000
> > > > > > RBP: ffff000000020000 R08: 0000000000000005 R09: 0000000000000000
> > > > > > R10: 0000000000000006 R11: 0000000000000000 R12: ffff000000000000
> > > > > > R13: ffff88814764cc00 R14: ffff000000000000 R15: ffff88814764cc00
> > > > > > FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> > > > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > > CR2: ffffdc0000000000 CR3: 000000000bc8e000 CR4: 00000000003506f0
> > > > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > > > > Call Trace:
> > > > > > <TASK>
> > > > > > strnlen include/linux/fortify-string.h:119 [inline]
> > > > > > copy_string_kernel+0x26/0x250 fs/exec.c:616
> > > > > > copy_strings_kernel+0xb3/0x190 fs/exec.c:655
> > > > > > kernel_execve+0x377/0x500 fs/exec.c:1998
> > > > > > call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
> > > > > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
> > > > > > </TASK>
> > > [...]
> > > > > > ---
> > > > > > 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.
> >
> > --
> > Kees Cook
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/YvWaqhLGsBp9ynIq%40iweiny-desk3.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve
2022-08-12 9:29 ` Dmitry Vyukov
@ 2022-08-12 18:44 ` Kees Cook
0 siblings, 0 replies; 8+ messages in thread
From: Kees Cook @ 2022-08-12 18:44 UTC (permalink / raw)
To: Dmitry Vyukov
Cc: Ira Weiny, Fabio M. De Francesco, ebiederm, linux-fsdevel,
linux-kernel, linux-mm, linux-next, sfr, syzkaller-bugs, viro,
syzbot
On Fri, Aug 12, 2022 at 11:29:44AM +0200, Dmitry Vyukov wrote:
> On Fri, 12 Aug 2022 at 02:11, Ira Weiny <ira.weiny@intel.com> wrote:
> >
> > On Thu, Aug 11, 2022 at 02:00:59PM -0700, Kees Cook wrote:
> > > On Thu, Aug 11, 2022 at 11:51:34AM -0700, Ira Weiny wrote:
> > > > On Thu, Aug 11, 2022 at 10:39:29AM -0700, Ira wrote:
> > > > > On Thu, Aug 11, 2022 at 08:33:16AM -0700, Kees Cook wrote:
> > > > > > Hi Fabio,
> > > > > >
> > > > > > It seems likely that the kmap change[1] might be causing this crash. Is
> > > > > > there a boot-time setup race between kmap being available and early umh
> > > > > > usage?
> > > > >
> > > > > I don't see how this is a setup problem with the config reported here.
> > > > >
> > > > > CONFIG_64BIT=y
> > > > >
> > > > > ...and HIGHMEM is not set.
> > > > > ...and PREEMPT_RT is not set.
> > > > >
> > > > > So the kmap_local_page() call in that stack should be a page_address() only.
> > > > >
> > > > > I think the issue must be some sort of race which was being prevented because
> > > > > of the preemption and/or pagefault disable built into kmap_atomic().
> > > > >
> > > > > Is this reproducable?
> > > > >
> > > > > The hunk below will surely fix it but I think the pagefault_disable() is
> > > > > the only thing that is required. It would be nice to test it.
> > > >
> > > > Fabio and I discussed this. And he also mentioned that pagefault_disable() is
> > > > all that is required.
> > >
> > > Okay, sounds good.
> > >
> > > > Do we have a way to test this?
> > >
> > > It doesn't look like syzbot has a reproducer yet, so its patch testing
> > > system[1] will not work. But if you can send me a patch, I could land it
> > > in -next and we could see if the reproduction frequency drops to zero.
> > > (Looking at the dashboard, it's seen 2 crashes, most recently 8 hours
> > > ago.)
> >
> > Patch sent.
> >
> > https://lore.kernel.org/lkml/20220812000919.408614-1-ira.weiny@intel.com/
Thank you!
> >
> > But I'm more confused after looking at this again.
>
> There is splat of random crashes in linux-next happened at the same time:
>
> https://groups.google.com/g/syzkaller-bugs/search?q=%22linux-next%20boot%20error%3A%22
>
> There are 10 different crashes in completely random places.
> I would assume they have the same root cause, some silent memory
> corruption or something similar.
Yeah, I noticed the crashes stopped "on their own", so I think I'll
wait a bit more, and if it start back up, we can try Ira's patch, though
I'd agree with the assessment that it looks like it shouldn't be needed.
-Kees
--
Kees Cook
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-08-12 18:44 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-08-11 7:29 [syzbot] linux-next boot error: BUG: unable to handle kernel paging request in kernel_execve syzbot
2022-08-11 15:33 ` Kees Cook
2022-08-11 17:39 ` Ira Weiny
2022-08-11 18:51 ` Ira Weiny
2022-08-11 21:00 ` Kees Cook
2022-08-12 0:11 ` Ira Weiny
2022-08-12 9:29 ` Dmitry Vyukov
2022-08-12 18:44 ` Kees Cook
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