* BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter
@ 2019-02-21 14:52 ` syzbot
0 siblings, 0 replies; 12+ messages in thread
From: syzbot @ 2019-02-21 14:52 UTC (permalink / raw)
To: akpm, amir73il, darrick.wong, david, hannes, hughd, jrdr.linux,
linux-kernel, linux-mm, syzkaller-bugs, willy
Hello,
syzbot found the following crash on:
HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
Unfortunately, I don't have any reproducer for this crash yet.
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
#PF error: [INSTR]
PGD a7ea0067 P4D a7ea0067 PUD 81535067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 15924 Comm: syz-executor0 Not tainted 5.0.0-rc4+ #50
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010: (null)
Code: Bad RIP value.
RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000814ac000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__generic_file_write_iter+0x25e/0x630 mm/filemap.c:3333
ext4_file_write_iter+0x37a/0x1410 fs/ext4/file.c:266
call_write_iter include/linux/fs.h:1862 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x764/0xb40 fs/read_write.c:487
vfs_write+0x20c/0x580 fs/read_write.c:549
ksys_write+0x105/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458089
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f3456db3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458089
RDX: 000000000000005b RSI: 0000000020000240 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3456db46d4
R13: 00000000004c7450 R14: 00000000004dce68 R15: 00000000ffffffff
Modules linked in:
CR2: 0000000000000000
---[ end trace 5cac9d2c75a59916 ]---
kobject: 'loop5' (000000004426a409): kobject_uevent_env
RIP: 0010: (null)
Code: Bad RIP value.
RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
kobject: 'loop5' (000000004426a409): fill_kobj_path: path
= '/devices/virtual/block/loop5'
RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
kobject: 'loop2' (00000000b82e0c58): kobject_uevent_env
kobject: 'loop2' (00000000b82e0c58): fill_kobj_path: path
= '/devices/virtual/block/loop2'
RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
kobject: 'loop5' (000000004426a409): kobject_uevent_env
FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
kobject: 'loop5' (000000004426a409): fill_kobj_path: path
= '/devices/virtual/block/loop5'
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000022029a0 CR3: 00000000814ac000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
---
This bug 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 bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.
^ permalink raw reply [flat|nested] 12+ messages in thread
* BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter
@ 2019-02-21 14:52 ` syzbot
0 siblings, 0 replies; 12+ messages in thread
From: syzbot @ 2019-02-21 14:52 UTC (permalink / raw)
To: akpm, amir73il, darrick.wong, david, hannes, hughd, jrdr.linux,
linux-kernel, linux-mm, syzkaller-bugs, willy
Hello,
syzbot found the following crash on:
HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
Unfortunately, I don't have any reproducer for this crash yet.
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
#PF error: [INSTR]
PGD a7ea0067 P4D a7ea0067 PUD 81535067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 15924 Comm: syz-executor0 Not tainted 5.0.0-rc4+ #50
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010: (null)
Code: Bad RIP value.
RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000814ac000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__generic_file_write_iter+0x25e/0x630 mm/filemap.c:3333
ext4_file_write_iter+0x37a/0x1410 fs/ext4/file.c:266
call_write_iter include/linux/fs.h:1862 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x764/0xb40 fs/read_write.c:487
vfs_write+0x20c/0x580 fs/read_write.c:549
ksys_write+0x105/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458089
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f3456db3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458089
RDX: 000000000000005b RSI: 0000000020000240 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3456db46d4
R13: 00000000004c7450 R14: 00000000004dce68 R15: 00000000ffffffff
Modules linked in:
CR2: 0000000000000000
---[ end trace 5cac9d2c75a59916 ]---
kobject: 'loop5' (000000004426a409): kobject_uevent_env
RIP: 0010: (null)
Code: Bad RIP value.
RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
kobject: 'loop5' (000000004426a409): fill_kobj_path: path
= '/devices/virtual/block/loop5'
RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
kobject: 'loop2' (00000000b82e0c58): kobject_uevent_env
kobject: 'loop2' (00000000b82e0c58): fill_kobj_path: path
= '/devices/virtual/block/loop2'
RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
kobject: 'loop5' (000000004426a409): kobject_uevent_env
FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
kobject: 'loop5' (000000004426a409): fill_kobj_path: path
= '/devices/virtual/block/loop5'
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000022029a0 CR3: 00000000814ac000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
---
This bug 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 bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter
2019-02-21 14:52 ` syzbot
(?)
@ 2019-02-21 19:36 ` Andrew Morton
2019-02-27 23:13 ` Jann Horn
2019-03-01 3:31 ` BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter Josh Poimboeuf
-1 siblings, 2 replies; 12+ messages in thread
From: Andrew Morton @ 2019-02-21 19:36 UTC (permalink / raw)
To: syzbot
Cc: amir73il, darrick.wong, david, hannes, hughd, jrdr.linux,
linux-kernel, linux-mm, syzkaller-bugs, willy, Jan Kara
On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
Not understanding. That seems to be saying that we got a NULL pointer
deref in __generic_file_write_iter() at
written = generic_perform_write(file, from, iocb->ki_pos);
which isn't possible.
I'm not seeing recent changes in there which could have caused this. Help.
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> #PF error: [INSTR]
> PGD a7ea0067 P4D a7ea0067 PUD 81535067 PMD 0
> Oops: 0010 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 15924 Comm: syz-executor0 Not tainted 5.0.0-rc4+ #50
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010: (null)
> Code: Bad RIP value.
> RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
> RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
> RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
> R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
> R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
> FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffffffffffffd6 CR3: 00000000814ac000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3333
> ext4_file_write_iter+0x37a/0x1410 fs/ext4/file.c:266
> call_write_iter include/linux/fs.h:1862 [inline]
> new_sync_write fs/read_write.c:474 [inline]
> __vfs_write+0x764/0xb40 fs/read_write.c:487
> vfs_write+0x20c/0x580 fs/read_write.c:549
> ksys_write+0x105/0x260 fs/read_write.c:598
> __do_sys_write fs/read_write.c:610 [inline]
> __se_sys_write fs/read_write.c:607 [inline]
> __x64_sys_write+0x73/0xb0 fs/read_write.c:607
> do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x458089
> Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f3456db3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458089
> RDX: 000000000000005b RSI: 0000000020000240 RDI: 0000000000000003
> RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3456db46d4
> R13: 00000000004c7450 R14: 00000000004dce68 R15: 00000000ffffffff
> Modules linked in:
> CR2: 0000000000000000
> ---[ end trace 5cac9d2c75a59916 ]---
> kobject: 'loop5' (000000004426a409): kobject_uevent_env
> RIP: 0010: (null)
> Code: Bad RIP value.
> RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
> kobject: 'loop5' (000000004426a409): fill_kobj_path: path
> = '/devices/virtual/block/loop5'
> RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
> kobject: 'loop2' (00000000b82e0c58): kobject_uevent_env
> kobject: 'loop2' (00000000b82e0c58): fill_kobj_path: path
> = '/devices/virtual/block/loop2'
> RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
> R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
> R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
> kobject: 'loop5' (000000004426a409): kobject_uevent_env
> FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> kobject: 'loop5' (000000004426a409): fill_kobj_path: path
> = '/devices/virtual/block/loop5'
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000022029a0 CR3: 00000000814ac000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>
>
> ---
> This bug 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 bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
^ permalink raw reply [flat|nested] 12+ messages in thread
* missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter]
2019-02-21 19:36 ` Andrew Morton
@ 2019-02-27 23:13 ` Jann Horn
2019-03-01 3:31 ` BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter Josh Poimboeuf
1 sibling, 0 replies; 12+ messages in thread
From: Jann Horn @ 2019-02-27 23:13 UTC (permalink / raw)
To: Andrew Morton, Josh Poimboeuf
Cc: syzbot, amir73il, Darrick J. Wong, Dave Chinner, hannes,
Hugh Dickins, jrdr.linux, kernel list, Linux-MM, syzkaller-bugs,
Matthew Wilcox, Jan Kara, the arch/x86 maintainers
+Josh for unwinding, +x86 folks
On Wed, Feb 27, 2019 at 11:43 PM Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
>
> Not understanding. That seems to be saying that we got a NULL pointer
> deref in __generic_file_write_iter() at
>
> written = generic_perform_write(file, from, iocb->ki_pos);
>
> which isn't possible.
>
> I'm not seeing recent changes in there which could have caused this. Help.
+
Maybe the problem is that the frame pointer unwinder isn't designed to
cope with NULL function pointers - or more generally, with an
unwinding operation that starts before the function's frame pointer
has been set up?
Unwinding starts at show_trace_log_lvl(). That begins with
unwind_start(), which calls __unwind_start(), which uses
get_frame_pointer(), which just returns regs->bp. But that frame
pointer points to the part of the stack that's storing the address of
the caller of the function that called NULL; the caller of NULL is
skipped, as far as I can tell.
What's kind of annoying here is that we don't have a proper frame set
up yet, we only have half a stack frame (saved RIP but no saved RBP).
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com
> >
> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> > #PF error: [INSTR]
> > PGD a7ea0067 P4D a7ea0067 PUD 81535067 PMD 0
> > Oops: 0010 [#1] PREEMPT SMP KASAN
> > CPU: 0 PID: 15924 Comm: syz-executor0 Not tainted 5.0.0-rc4+ #50
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > RIP: 0010: (null)
> > Code: Bad RIP value.
> > RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
> > RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
> > RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
> > RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
> > R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
> > R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
> > FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: ffffffffffffffd6 CR3: 00000000814ac000 CR4: 00000000001406f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> > __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3333
> > ext4_file_write_iter+0x37a/0x1410 fs/ext4/file.c:266
> > call_write_iter include/linux/fs.h:1862 [inline]
> > new_sync_write fs/read_write.c:474 [inline]
> > __vfs_write+0x764/0xb40 fs/read_write.c:487
> > vfs_write+0x20c/0x580 fs/read_write.c:549
> > ksys_write+0x105/0x260 fs/read_write.c:598
> > __do_sys_write fs/read_write.c:610 [inline]
> > __se_sys_write fs/read_write.c:607 [inline]
> > __x64_sys_write+0x73/0xb0 fs/read_write.c:607
> > do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
> > entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x458089
> > Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> > 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> > ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> > RSP: 002b:00007f3456db3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458089
> > RDX: 000000000000005b RSI: 0000000020000240 RDI: 0000000000000003
> > RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3456db46d4
> > R13: 00000000004c7450 R14: 00000000004dce68 R15: 00000000ffffffff
> > Modules linked in:
> > CR2: 0000000000000000
> > ---[ end trace 5cac9d2c75a59916 ]---
> > kobject: 'loop5' (000000004426a409): kobject_uevent_env
> > RIP: 0010: (null)
> > Code: Bad RIP value.
> > RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
> > RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
> > kobject: 'loop5' (000000004426a409): fill_kobj_path: path
> > = '/devices/virtual/block/loop5'
> > RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
> > kobject: 'loop2' (00000000b82e0c58): kobject_uevent_env
> > kobject: 'loop2' (00000000b82e0c58): fill_kobj_path: path
> > = '/devices/virtual/block/loop2'
> > RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
> > R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
> > R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
> > kobject: 'loop5' (000000004426a409): kobject_uevent_env
> > FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> > kobject: 'loop5' (000000004426a409): fill_kobj_path: path
> > = '/devices/virtual/block/loop5'
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000022029a0 CR3: 00000000814ac000 CR4: 00000000001406f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >
> >
> > ---
> > This bug 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 bug report. See:
> > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> > syzbot.
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter]
@ 2019-02-27 23:13 ` Jann Horn
0 siblings, 0 replies; 12+ messages in thread
From: Jann Horn @ 2019-02-27 23:13 UTC (permalink / raw)
To: Andrew Morton, Josh Poimboeuf
Cc: syzbot, amir73il, Darrick J. Wong, Dave Chinner, hannes,
Hugh Dickins, jrdr.linux, kernel list, Linux-MM, syzkaller-bugs,
Matthew Wilcox, Jan Kara, the arch/x86 maintainers
+Josh for unwinding, +x86 folks
On Wed, Feb 27, 2019 at 11:43 PM Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
>
> Not understanding. That seems to be saying that we got a NULL pointer
> deref in __generic_file_write_iter() at
>
> written = generic_perform_write(file, from, iocb->ki_pos);
>
> which isn't possible.
>
> I'm not seeing recent changes in there which could have caused this. Help.
+
Maybe the problem is that the frame pointer unwinder isn't designed to
cope with NULL function pointers - or more generally, with an
unwinding operation that starts before the function's frame pointer
has been set up?
Unwinding starts at show_trace_log_lvl(). That begins with
unwind_start(), which calls __unwind_start(), which uses
get_frame_pointer(), which just returns regs->bp. But that frame
pointer points to the part of the stack that's storing the address of
the caller of the function that called NULL; the caller of NULL is
skipped, as far as I can tell.
What's kind of annoying here is that we don't have a proper frame set
up yet, we only have half a stack frame (saved RIP but no saved RBP).
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com
> >
> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> > #PF error: [INSTR]
> > PGD a7ea0067 P4D a7ea0067 PUD 81535067 PMD 0
> > Oops: 0010 [#1] PREEMPT SMP KASAN
> > CPU: 0 PID: 15924 Comm: syz-executor0 Not tainted 5.0.0-rc4+ #50
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > RIP: 0010: (null)
> > Code: Bad RIP value.
> > RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
> > RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
> > RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
> > RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
> > R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
> > R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
> > FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: ffffffffffffffd6 CR3: 00000000814ac000 CR4: 00000000001406f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> > __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3333
> > ext4_file_write_iter+0x37a/0x1410 fs/ext4/file.c:266
> > call_write_iter include/linux/fs.h:1862 [inline]
> > new_sync_write fs/read_write.c:474 [inline]
> > __vfs_write+0x764/0xb40 fs/read_write.c:487
> > vfs_write+0x20c/0x580 fs/read_write.c:549
> > ksys_write+0x105/0x260 fs/read_write.c:598
> > __do_sys_write fs/read_write.c:610 [inline]
> > __se_sys_write fs/read_write.c:607 [inline]
> > __x64_sys_write+0x73/0xb0 fs/read_write.c:607
> > do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
> > entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x458089
> > Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> > 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> > ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> > RSP: 002b:00007f3456db3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458089
> > RDX: 000000000000005b RSI: 0000000020000240 RDI: 0000000000000003
> > RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3456db46d4
> > R13: 00000000004c7450 R14: 00000000004dce68 R15: 00000000ffffffff
> > Modules linked in:
> > CR2: 0000000000000000
> > ---[ end trace 5cac9d2c75a59916 ]---
> > kobject: 'loop5' (000000004426a409): kobject_uevent_env
> > RIP: 0010: (null)
> > Code: Bad RIP value.
> > RSP: 0018:ffff88804c3d7858 EFLAGS: 00010246
> > RAX: 0000000000000000 RBX: ffffffff885aeb60 RCX: 000000000000005b
> > kobject: 'loop5' (000000004426a409): fill_kobj_path: path
> > = '/devices/virtual/block/loop5'
> > RDX: 0000000000000000 RSI: ffff88807ec22930 RDI: ffff8880a59bdcc0
> > kobject: 'loop2' (00000000b82e0c58): kobject_uevent_env
> > kobject: 'loop2' (00000000b82e0c58): fill_kobj_path: path
> > = '/devices/virtual/block/loop2'
> > RBP: ffff88804c3d79b8 R08: 0000000000000000 R09: ffff88804c3d7910
> > R10: ffff8880835ca200 R11: 0000000000000000 R12: 000000000000005b
> > R13: ffff88804c3d7c98 R14: dffffc0000000000 R15: 0000000000000000
> > kobject: 'loop5' (000000004426a409): kobject_uevent_env
> > FS: 00007f3456db4700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> > kobject: 'loop5' (000000004426a409): fill_kobj_path: path
> > = '/devices/virtual/block/loop5'
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000022029a0 CR3: 00000000814ac000 CR4: 00000000001406f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >
> >
> > ---
> > This bug 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 bug report. See:
> > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> > syzbot.
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter]
2019-02-27 23:13 ` Jann Horn
@ 2019-02-28 12:56 ` Thomas Gleixner
-1 siblings, 0 replies; 12+ messages in thread
From: Thomas Gleixner @ 2019-02-28 12:56 UTC (permalink / raw)
To: Jann Horn
Cc: Andrew Morton, Josh Poimboeuf, syzbot, amir73il, Darrick J. Wong,
Dave Chinner, hannes, Hugh Dickins, jrdr.linux, kernel list,
Linux-MM, syzkaller-bugs, Matthew Wilcox, Jan Kara,
the arch/x86 maintainers
On Thu, 28 Feb 2019, Jann Horn wrote:
> +Josh for unwinding, +x86 folks
> On Wed, Feb 27, 2019 at 11:43 PM Andrew Morton
> <akpm@linux-foundation.org> wrote:
> > On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> > > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > > git tree: upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > >
> > > Unfortunately, I don't have any reproducer for this crash yet.
> >
> > Not understanding. That seems to be saying that we got a NULL pointer
> > deref in __generic_file_write_iter() at
> >
> > written = generic_perform_write(file, from, iocb->ki_pos);
> >
> > which isn't possible.
> >
> > I'm not seeing recent changes in there which could have caused this. Help.
>
> +
>
> Maybe the problem is that the frame pointer unwinder isn't designed to
> cope with NULL function pointers - or more generally, with an
> unwinding operation that starts before the function's frame pointer
> has been set up?
>
> Unwinding starts at show_trace_log_lvl(). That begins with
> unwind_start(), which calls __unwind_start(), which uses
> get_frame_pointer(), which just returns regs->bp. But that frame
> pointer points to the part of the stack that's storing the address of
> the caller of the function that called NULL; the caller of NULL is
> skipped, as far as I can tell.
>
> What's kind of annoying here is that we don't have a proper frame set
> up yet, we only have half a stack frame (saved RIP but no saved RBP).
That wreckage is related to the fact that the indirect calls are going
through __x86_indirect_thunk_$REG. I just verified on a VM with some other
callback NULL'ed that the resulting backtrace is not really helpful.
So in that case generic_perform_write() has two indirect calls:
mapping->a_ops->write_begin() and ->write_end()
Thanks,
tglx
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter]
@ 2019-02-28 12:56 ` Thomas Gleixner
0 siblings, 0 replies; 12+ messages in thread
From: Thomas Gleixner @ 2019-02-28 12:56 UTC (permalink / raw)
To: Jann Horn
Cc: Andrew Morton, Josh Poimboeuf, syzbot, amir73il, Darrick J. Wong,
Dave Chinner, hannes, Hugh Dickins, jrdr.linux, kernel list,
Linux-MM, syzkaller-bugs, Matthew Wilcox, Jan Kara,
the arch/x86 maintainers
On Thu, 28 Feb 2019, Jann Horn wrote:
> +Josh for unwinding, +x86 folks
> On Wed, Feb 27, 2019 at 11:43 PM Andrew Morton
> <akpm@linux-foundation.org> wrote:
> > On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> > > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > > git tree: upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > >
> > > Unfortunately, I don't have any reproducer for this crash yet.
> >
> > Not understanding. That seems to be saying that we got a NULL pointer
> > deref in __generic_file_write_iter() at
> >
> > written = generic_perform_write(file, from, iocb->ki_pos);
> >
> > which isn't possible.
> >
> > I'm not seeing recent changes in there which could have caused this. Help.
>
> +
>
> Maybe the problem is that the frame pointer unwinder isn't designed to
> cope with NULL function pointers - or more generally, with an
> unwinding operation that starts before the function's frame pointer
> has been set up?
>
> Unwinding starts at show_trace_log_lvl(). That begins with
> unwind_start(), which calls __unwind_start(), which uses
> get_frame_pointer(), which just returns regs->bp. But that frame
> pointer points to the part of the stack that's storing the address of
> the caller of the function that called NULL; the caller of NULL is
> skipped, as far as I can tell.
>
> What's kind of annoying here is that we don't have a proper frame set
> up yet, we only have half a stack frame (saved RIP but no saved RBP).
That wreckage is related to the fact that the indirect calls are going
through __x86_indirect_thunk_$REG. I just verified on a VM with some other
callback NULL'ed that the resulting backtrace is not really helpful.
So in that case generic_perform_write() has two indirect calls:
mapping->a_ops->write_begin() and ->write_end()
Thanks,
tglx
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter]
2019-02-28 12:56 ` Thomas Gleixner
@ 2019-02-28 16:34 ` Jann Horn
-1 siblings, 0 replies; 12+ messages in thread
From: Jann Horn @ 2019-02-28 16:34 UTC (permalink / raw)
To: Thomas Gleixner
Cc: Andrew Morton, Josh Poimboeuf, syzbot, amir73il, Darrick J. Wong,
Dave Chinner, hannes, Hugh Dickins, jrdr.linux, kernel list,
Linux-MM, syzkaller-bugs, Matthew Wilcox, Jan Kara,
the arch/x86 maintainers
On Thu, Feb 28, 2019 at 1:57 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> On Thu, 28 Feb 2019, Jann Horn wrote:
> > +Josh for unwinding, +x86 folks
> > On Wed, Feb 27, 2019 at 11:43 PM Andrew Morton
> > <akpm@linux-foundation.org> wrote:
> > > On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
> > >
> > > > Hello,
> > > >
> > > > syzbot found the following crash on:
> > > >
> > > > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > > > git tree: upstream
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > > >
> > > > Unfortunately, I don't have any reproducer for this crash yet.
> > >
> > > Not understanding. That seems to be saying that we got a NULL pointer
> > > deref in __generic_file_write_iter() at
> > >
> > > written = generic_perform_write(file, from, iocb->ki_pos);
> > >
> > > which isn't possible.
> > >
> > > I'm not seeing recent changes in there which could have caused this. Help.
> >
> > +
> >
> > Maybe the problem is that the frame pointer unwinder isn't designed to
> > cope with NULL function pointers - or more generally, with an
> > unwinding operation that starts before the function's frame pointer
> > has been set up?
> >
> > Unwinding starts at show_trace_log_lvl(). That begins with
> > unwind_start(), which calls __unwind_start(), which uses
> > get_frame_pointer(), which just returns regs->bp. But that frame
> > pointer points to the part of the stack that's storing the address of
> > the caller of the function that called NULL; the caller of NULL is
> > skipped, as far as I can tell.
> >
> > What's kind of annoying here is that we don't have a proper frame set
> > up yet, we only have half a stack frame (saved RIP but no saved RBP).
>
> That wreckage is related to the fact that the indirect calls are going
> through __x86_indirect_thunk_$REG. I just verified on a VM with some other
> callback NULL'ed that the resulting backtrace is not really helpful.
>
> So in that case generic_perform_write() has two indirect calls:
>
> mapping->a_ops->write_begin() and ->write_end()
Does the indirect thunk thing really make any difference? When you
arrive at RIP=NULL, RSP points to a saved instruction pointer, just
like when indirect calls are compiled normally.
I just compiled kernels with artificial calls to a NULL function
pointer (in prctl_set_seccomp()), with retpoline disabled, with both
unwinders. The ORC unwinder shows a call trace with "?" everywhere
that doesn't show the caller:
[ 228.219140] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000000
[ 228.223897] #PF error: [INSTR]
[ 228.224562] PGD 0 P4D 0
[ 228.225119] Oops: 0010 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
[ 228.226319] CPU: 1 PID: 1099 Comm: artificial_null Not tainted
5.0.0-rc8+ #299
[ 228.227818] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1 04/01/2014
[ 228.229542] RIP: 0010: (null)
[ 228.230331] Code: Bad RIP value.
[ 228.231011] RSP: 0018:ffff8881d798fe88 EFLAGS: 00010246
[ 228.232104] RAX: ffffffffffffffda RBX: 0000000000000016 RCX: ffffffffa0368205
[ 228.233599] RDX: dffffc0000000000 RSI: 00007ffde0d71168 RDI: 0000000000000042
[ 228.235077] RBP: 1ffff1103af31fd4 R08: 0000561b50807740 R09: 0000000000000016
[ 228.236557] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000042
[ 228.238039] R13: 0000000000000000 R14: 00007ffde0d71168 R15: 0000561b50807740
[ 228.239517] FS: 00007fe31f1cf700(0000) GS:ffff8881eb040000(0000)
knlGS:0000000000000000
[ 228.241213] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 228.242411] CR2: ffffffffffffffd6 CR3: 00000001df8b8004 CR4: 0000000000360ee0
[ 228.243886] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 228.245364] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 228.246841] Call Trace:
[ 228.247366] ? __x64_sys_prctl+0x402/0x680
[ 228.248224] ? __ia32_sys_prctl+0x6e0/0x6e0
[ 228.249106] ? __do_page_fault+0x457/0x620
[ 228.249969] ? do_syscall_64+0x6d/0x160
[ 228.250778] ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
[...]
whereas the FP unwinder shows this, listing prctl_set_seccomp only
with a question mark:
[ 47.469957] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000000
[ 47.476973] #PF error: [INSTR]
[ 47.477742] PGD 0 P4D 0
[ 47.478341] Oops: 0010 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
[ 47.479703] CPU: 4 PID: 1079 Comm: artificial_null Not tainted
5.0.0-rc8+ #300
[ 47.481489] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1 04/01/2014
[ 47.483442] RIP: 0010: (null)
[ 47.484328] Code: Bad RIP value.
[ 47.485085] RSP: 0018:ffff8881e01f7e70 EFLAGS: 00010246
[ 47.486358] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: ffffffffafbf007a
[ 47.488090] RDX: dffffc0000000000 RSI: 00007ffe164b4f28 RDI: 0000000000000042
[ 47.489862] RBP: ffff8881e01f7e78 R08: 0000562942136740 R09: 0000000000000016
[ 47.491491] R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1103c03efd3
[ 47.493144] R13: 0000000000000042 R14: 00007ffe164b4f28 R15: 0000000000000016
[ 47.494795] FS: 00007fa38b1d6700(0000) GS:ffff8881eb300000(0000)
knlGS:0000000000000000
[ 47.496638] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 47.497981] CR2: ffffffffffffffd6 CR3: 00000001e0e4c006 CR4: 0000000000360ee0
[ 47.499623] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 47.501252] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 47.502927] Call Trace:
[ 47.503501] ? prctl_set_seccomp+0x3a/0x50
[ 47.504450] __x64_sys_prctl+0x457/0x6f0
[ 47.505349] ? __ia32_sys_prctl+0x750/0x750
[ 47.506352] do_syscall_64+0x72/0x160
[ 47.507214] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[...]
Looking back at the syzkaller report, the command line output
(https://syzkaller.appspot.com/x/log.txt?x=1101382f400000) has this:
[ 375.092788] Call Trace:
[ 375.095378] ? generic_perform_write+0x2a0/0x6b0
[ 375.100150] ? add_page_wait_queue+0x480/0x480
[ 375.104744] ? current_time+0x1b0/0x1b0
[ 375.108727] ? generic_write_check_limits+0x380/0x380
[ 375.113942] ? ext4_file_write_iter+0x28b/0x1410
{some non-dmesg output here}
[ 375.118711] __generic_file_write_iter+0x25e/0x630
[ 375.123714] ext4_file_write_iter+0x37a/0x1410
The first entry with a question mark is *RSP, the real caller; that's
generic_perform_write(), as expected. The rest is probably just random
garbage that happened to still be on the stack. It looks like
syzkaller strips out trace elements with question marks in front.
So I think this doesn't really have anything to do with
__x86_indirect_thunk_$REG, and the best possible fix might be to teach
the unwinders that RIP==NULL means "pretend that RIP is *real_RSP and
that RSP is real_RSP+8, and report *real_RSP as the first element of
the backtrace".
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter]
@ 2019-02-28 16:34 ` Jann Horn
0 siblings, 0 replies; 12+ messages in thread
From: Jann Horn @ 2019-02-28 16:34 UTC (permalink / raw)
To: Thomas Gleixner
Cc: Andrew Morton, Josh Poimboeuf, syzbot, amir73il, Darrick J. Wong,
Dave Chinner, hannes, Hugh Dickins, jrdr.linux, kernel list,
Linux-MM, syzkaller-bugs, Matthew Wilcox, Jan Kara,
the arch/x86 maintainers
On Thu, Feb 28, 2019 at 1:57 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> On Thu, 28 Feb 2019, Jann Horn wrote:
> > +Josh for unwinding, +x86 folks
> > On Wed, Feb 27, 2019 at 11:43 PM Andrew Morton
> > <akpm@linux-foundation.org> wrote:
> > > On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
> > >
> > > > Hello,
> > > >
> > > > syzbot found the following crash on:
> > > >
> > > > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > > > git tree: upstream
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > > >
> > > > Unfortunately, I don't have any reproducer for this crash yet.
> > >
> > > Not understanding. That seems to be saying that we got a NULL pointer
> > > deref in __generic_file_write_iter() at
> > >
> > > written = generic_perform_write(file, from, iocb->ki_pos);
> > >
> > > which isn't possible.
> > >
> > > I'm not seeing recent changes in there which could have caused this. Help.
> >
> > +
> >
> > Maybe the problem is that the frame pointer unwinder isn't designed to
> > cope with NULL function pointers - or more generally, with an
> > unwinding operation that starts before the function's frame pointer
> > has been set up?
> >
> > Unwinding starts at show_trace_log_lvl(). That begins with
> > unwind_start(), which calls __unwind_start(), which uses
> > get_frame_pointer(), which just returns regs->bp. But that frame
> > pointer points to the part of the stack that's storing the address of
> > the caller of the function that called NULL; the caller of NULL is
> > skipped, as far as I can tell.
> >
> > What's kind of annoying here is that we don't have a proper frame set
> > up yet, we only have half a stack frame (saved RIP but no saved RBP).
>
> That wreckage is related to the fact that the indirect calls are going
> through __x86_indirect_thunk_$REG. I just verified on a VM with some other
> callback NULL'ed that the resulting backtrace is not really helpful.
>
> So in that case generic_perform_write() has two indirect calls:
>
> mapping->a_ops->write_begin() and ->write_end()
Does the indirect thunk thing really make any difference? When you
arrive at RIP=NULL, RSP points to a saved instruction pointer, just
like when indirect calls are compiled normally.
I just compiled kernels with artificial calls to a NULL function
pointer (in prctl_set_seccomp()), with retpoline disabled, with both
unwinders. The ORC unwinder shows a call trace with "?" everywhere
that doesn't show the caller:
[ 228.219140] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000000
[ 228.223897] #PF error: [INSTR]
[ 228.224562] PGD 0 P4D 0
[ 228.225119] Oops: 0010 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
[ 228.226319] CPU: 1 PID: 1099 Comm: artificial_null Not tainted
5.0.0-rc8+ #299
[ 228.227818] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1 04/01/2014
[ 228.229542] RIP: 0010: (null)
[ 228.230331] Code: Bad RIP value.
[ 228.231011] RSP: 0018:ffff8881d798fe88 EFLAGS: 00010246
[ 228.232104] RAX: ffffffffffffffda RBX: 0000000000000016 RCX: ffffffffa0368205
[ 228.233599] RDX: dffffc0000000000 RSI: 00007ffde0d71168 RDI: 0000000000000042
[ 228.235077] RBP: 1ffff1103af31fd4 R08: 0000561b50807740 R09: 0000000000000016
[ 228.236557] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000042
[ 228.238039] R13: 0000000000000000 R14: 00007ffde0d71168 R15: 0000561b50807740
[ 228.239517] FS: 00007fe31f1cf700(0000) GS:ffff8881eb040000(0000)
knlGS:0000000000000000
[ 228.241213] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 228.242411] CR2: ffffffffffffffd6 CR3: 00000001df8b8004 CR4: 0000000000360ee0
[ 228.243886] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 228.245364] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 228.246841] Call Trace:
[ 228.247366] ? __x64_sys_prctl+0x402/0x680
[ 228.248224] ? __ia32_sys_prctl+0x6e0/0x6e0
[ 228.249106] ? __do_page_fault+0x457/0x620
[ 228.249969] ? do_syscall_64+0x6d/0x160
[ 228.250778] ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
[...]
whereas the FP unwinder shows this, listing prctl_set_seccomp only
with a question mark:
[ 47.469957] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000000
[ 47.476973] #PF error: [INSTR]
[ 47.477742] PGD 0 P4D 0
[ 47.478341] Oops: 0010 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
[ 47.479703] CPU: 4 PID: 1079 Comm: artificial_null Not tainted
5.0.0-rc8+ #300
[ 47.481489] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1 04/01/2014
[ 47.483442] RIP: 0010: (null)
[ 47.484328] Code: Bad RIP value.
[ 47.485085] RSP: 0018:ffff8881e01f7e70 EFLAGS: 00010246
[ 47.486358] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: ffffffffafbf007a
[ 47.488090] RDX: dffffc0000000000 RSI: 00007ffe164b4f28 RDI: 0000000000000042
[ 47.489862] RBP: ffff8881e01f7e78 R08: 0000562942136740 R09: 0000000000000016
[ 47.491491] R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1103c03efd3
[ 47.493144] R13: 0000000000000042 R14: 00007ffe164b4f28 R15: 0000000000000016
[ 47.494795] FS: 00007fa38b1d6700(0000) GS:ffff8881eb300000(0000)
knlGS:0000000000000000
[ 47.496638] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 47.497981] CR2: ffffffffffffffd6 CR3: 00000001e0e4c006 CR4: 0000000000360ee0
[ 47.499623] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 47.501252] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 47.502927] Call Trace:
[ 47.503501] ? prctl_set_seccomp+0x3a/0x50
[ 47.504450] __x64_sys_prctl+0x457/0x6f0
[ 47.505349] ? __ia32_sys_prctl+0x750/0x750
[ 47.506352] do_syscall_64+0x72/0x160
[ 47.507214] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[...]
Looking back at the syzkaller report, the command line output
(https://syzkaller.appspot.com/x/log.txt?x=1101382f400000) has this:
[ 375.092788] Call Trace:
[ 375.095378] ? generic_perform_write+0x2a0/0x6b0
[ 375.100150] ? add_page_wait_queue+0x480/0x480
[ 375.104744] ? current_time+0x1b0/0x1b0
[ 375.108727] ? generic_write_check_limits+0x380/0x380
[ 375.113942] ? ext4_file_write_iter+0x28b/0x1410
{some non-dmesg output here}
[ 375.118711] __generic_file_write_iter+0x25e/0x630
[ 375.123714] ext4_file_write_iter+0x37a/0x1410
The first entry with a question mark is *RSP, the real caller; that's
generic_perform_write(), as expected. The rest is probably just random
garbage that happened to still be on the stack. It looks like
syzkaller strips out trace elements with question marks in front.
So I think this doesn't really have anything to do with
__x86_indirect_thunk_$REG, and the best possible fix might be to teach
the unwinders that RIP==NULL means "pretend that RIP is *real_RSP and
that RSP is real_RSP+8, and report *real_RSP as the first element of
the backtrace".
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter]
2019-02-28 16:34 ` Jann Horn
@ 2019-03-01 0:54 ` Jann Horn
-1 siblings, 0 replies; 12+ messages in thread
From: Jann Horn @ 2019-03-01 0:54 UTC (permalink / raw)
To: Thomas Gleixner
Cc: Andrew Morton, Josh Poimboeuf, syzbot, Amir Goldstein,
Darrick J. Wong, Dave Chinner, hannes, Hugh Dickins,
Souptick Joarder, kernel list, Linux-MM, syzkaller-bugs,
Matthew Wilcox, Jan Kara, the arch/x86 maintainers
On Thu, Feb 28, 2019 at 5:34 PM Jann Horn <jannh@google.com> wrote:
>
> On Thu, Feb 28, 2019 at 1:57 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Thu, 28 Feb 2019, Jann Horn wrote:
> > > +Josh for unwinding, +x86 folks
> > > On Wed, Feb 27, 2019 at 11:43 PM Andrew Morton
> > > <akpm@linux-foundation.org> wrote:
> > > > On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
> > > >
> > > > > Hello,
> > > > >
> > > > > syzbot found the following crash on:
> > > > >
> > > > > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > > > > git tree: upstream
> > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > > > >
> > > > > Unfortunately, I don't have any reproducer for this crash yet.
> > > >
> > > > Not understanding. That seems to be saying that we got a NULL pointer
> > > > deref in __generic_file_write_iter() at
> > > >
> > > > written = generic_perform_write(file, from, iocb->ki_pos);
> > > >
> > > > which isn't possible.
> > > >
> > > > I'm not seeing recent changes in there which could have caused this. Help.
> > >
> > > +
> > >
> > > Maybe the problem is that the frame pointer unwinder isn't designed to
> > > cope with NULL function pointers - or more generally, with an
> > > unwinding operation that starts before the function's frame pointer
> > > has been set up?
> > >
> > > Unwinding starts at show_trace_log_lvl(). That begins with
> > > unwind_start(), which calls __unwind_start(), which uses
> > > get_frame_pointer(), which just returns regs->bp. But that frame
> > > pointer points to the part of the stack that's storing the address of
> > > the caller of the function that called NULL; the caller of NULL is
> > > skipped, as far as I can tell.
> > >
> > > What's kind of annoying here is that we don't have a proper frame set
> > > up yet, we only have half a stack frame (saved RIP but no saved RBP).
> >
> > That wreckage is related to the fact that the indirect calls are going
> > through __x86_indirect_thunk_$REG. I just verified on a VM with some other
> > callback NULL'ed that the resulting backtrace is not really helpful.
> >
> > So in that case generic_perform_write() has two indirect calls:
> >
> > mapping->a_ops->write_begin() and ->write_end()
>
> Does the indirect thunk thing really make any difference? When you
> arrive at RIP=NULL, RSP points to a saved instruction pointer, just
> like when indirect calls are compiled normally.
>
> I just compiled kernels with artificial calls to a NULL function
> pointer (in prctl_set_seccomp()), with retpoline disabled, with both
> unwinders. The ORC unwinder shows a call trace with "?" everywhere
> that doesn't show the caller:
[...]
> So I think this doesn't really have anything to do with
> __x86_indirect_thunk_$REG, and the best possible fix might be to teach
> the unwinders that RIP==NULL means "pretend that RIP is *real_RSP and
> that RSP is real_RSP+8, and report *real_RSP as the first element of
> the backtrace".
Cooking up some patches now...
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter]
@ 2019-03-01 0:54 ` Jann Horn
0 siblings, 0 replies; 12+ messages in thread
From: Jann Horn @ 2019-03-01 0:54 UTC (permalink / raw)
To: Thomas Gleixner
Cc: Andrew Morton, Josh Poimboeuf, syzbot, Amir Goldstein,
Darrick J. Wong, Dave Chinner, hannes, Hugh Dickins,
Souptick Joarder, kernel list, Linux-MM, syzkaller-bugs,
Matthew Wilcox, Jan Kara, the arch/x86 maintainers
On Thu, Feb 28, 2019 at 5:34 PM Jann Horn <jannh@google.com> wrote:
>
> On Thu, Feb 28, 2019 at 1:57 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Thu, 28 Feb 2019, Jann Horn wrote:
> > > +Josh for unwinding, +x86 folks
> > > On Wed, Feb 27, 2019 at 11:43 PM Andrew Morton
> > > <akpm@linux-foundation.org> wrote:
> > > > On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
> > > >
> > > > > Hello,
> > > > >
> > > > > syzbot found the following crash on:
> > > > >
> > > > > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > > > > git tree: upstream
> > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > > > >
> > > > > Unfortunately, I don't have any reproducer for this crash yet.
> > > >
> > > > Not understanding. That seems to be saying that we got a NULL pointer
> > > > deref in __generic_file_write_iter() at
> > > >
> > > > written = generic_perform_write(file, from, iocb->ki_pos);
> > > >
> > > > which isn't possible.
> > > >
> > > > I'm not seeing recent changes in there which could have caused this. Help.
> > >
> > > +
> > >
> > > Maybe the problem is that the frame pointer unwinder isn't designed to
> > > cope with NULL function pointers - or more generally, with an
> > > unwinding operation that starts before the function's frame pointer
> > > has been set up?
> > >
> > > Unwinding starts at show_trace_log_lvl(). That begins with
> > > unwind_start(), which calls __unwind_start(), which uses
> > > get_frame_pointer(), which just returns regs->bp. But that frame
> > > pointer points to the part of the stack that's storing the address of
> > > the caller of the function that called NULL; the caller of NULL is
> > > skipped, as far as I can tell.
> > >
> > > What's kind of annoying here is that we don't have a proper frame set
> > > up yet, we only have half a stack frame (saved RIP but no saved RBP).
> >
> > That wreckage is related to the fact that the indirect calls are going
> > through __x86_indirect_thunk_$REG. I just verified on a VM with some other
> > callback NULL'ed that the resulting backtrace is not really helpful.
> >
> > So in that case generic_perform_write() has two indirect calls:
> >
> > mapping->a_ops->write_begin() and ->write_end()
>
> Does the indirect thunk thing really make any difference? When you
> arrive at RIP=NULL, RSP points to a saved instruction pointer, just
> like when indirect calls are compiled normally.
>
> I just compiled kernels with artificial calls to a NULL function
> pointer (in prctl_set_seccomp()), with retpoline disabled, with both
> unwinders. The ORC unwinder shows a call trace with "?" everywhere
> that doesn't show the caller:
[...]
> So I think this doesn't really have anything to do with
> __x86_indirect_thunk_$REG, and the best possible fix might be to teach
> the unwinders that RIP==NULL means "pretend that RIP is *real_RSP and
> that RSP is real_RSP+8, and report *real_RSP as the first element of
> the backtrace".
Cooking up some patches now...
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter
2019-02-21 19:36 ` Andrew Morton
2019-02-27 23:13 ` Jann Horn
@ 2019-03-01 3:31 ` Josh Poimboeuf
1 sibling, 0 replies; 12+ messages in thread
From: Josh Poimboeuf @ 2019-03-01 3:31 UTC (permalink / raw)
To: Andrew Morton
Cc: syzbot, amir73il, darrick.wong, david, hannes, hughd, jrdr.linux,
linux-kernel, linux-mm, syzkaller-bugs, willy, Jan Kara
On Thu, Feb 21, 2019 at 11:36:24AM -0800, Andrew Morton wrote:
> On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
>
> Not understanding. That seems to be saying that we got a NULL pointer
> deref in __generic_file_write_iter() at
>
> written = generic_perform_write(file, from, iocb->ki_pos);
>
> which isn't possible.
>
> I'm not seeing recent changes in there which could have caused this. Help.
FWIW, the panic happened in generic_perform_write() when it called
a_ops->write_begin, which was NULL.
I agree with Jann that the unwinders should handle this scenario better.
--
Josh
^ permalink raw reply [flat|nested] 12+ messages in thread
end of thread, other threads:[~2019-03-01 3:31 UTC | newest]
Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-02-21 14:52 BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter syzbot
2019-02-21 14:52 ` syzbot
2019-02-21 19:36 ` Andrew Morton
2019-02-27 23:13 ` missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter] Jann Horn
2019-02-27 23:13 ` Jann Horn
2019-02-28 12:56 ` Thomas Gleixner
2019-02-28 12:56 ` Thomas Gleixner
2019-02-28 16:34 ` Jann Horn
2019-02-28 16:34 ` Jann Horn
2019-03-01 0:54 ` Jann Horn
2019-03-01 0:54 ` Jann Horn
2019-03-01 3:31 ` BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter Josh Poimboeuf
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