Re: general protection fault in percpu_ref_exit

2020-10-08 Thread Ming Lei 
On Thu, Oct 08, 2020 at 07:23:02PM -0600, Jens Axboe wrote:
> On 10/8/20 2:28 PM, syzbot wrote:
> > syzbot has bisected this issue to:
> > 
> > commit 2b0d3d3e4fcfb19d10f9a82910b8f0f05c56ee3e
> > Author: Ming Lei 
> > Date:   Thu Oct 1 15:48:41 2020 +
> > 
> > percpu_ref: reduce memory footprint of percpu_ref in fast path
> > 
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=126930d050
> > start commit:   8b787da7 Add linux-next specific files for 20201007
> > git tree:   linux-next
> > final oops: https://syzkaller.appspot.com/x/report.txt?x=116930d050
> > console output: https://syzkaller.appspot.com/x/log.txt?x=166930d050
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=aac055e9c8fbd2b8
> > dashboard link: https://syzkaller.appspot.com/bug?extid=fd15ff734dace9e16437
> > syz repro:  https://syzkaller.appspot.com/x/repro.syz?x=119a056850
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=106c0a8b90
> > 
> > Reported-by: syzbot+fd15ff734dace9e16...@syzkaller.appspotmail.com
> > Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in 
> > fast path")
> > 
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> 
> Ming, this looks like a call of percpu_ref_exit() on a zeroed refs (that
> hasn't been initialized). Really a caller error imho, but might make sense
> to be a bit safer there.

Hello Jens,

The fix is sent out as:

https://lore.kernel.org/linux-block/20201009040356.43802-1-ming@redhat.com/T/#u

Sorry for making the trouble.

Thanks,
Ming

Re: general protection fault in percpu_ref_exit

2020-10-08 Thread Jens Axboe 
On 10/8/20 2:28 PM, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit 2b0d3d3e4fcfb19d10f9a82910b8f0f05c56ee3e
> Author: Ming Lei 
> Date:   Thu Oct 1 15:48:41 2020 +
> 
> percpu_ref: reduce memory footprint of percpu_ref in fast path
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=126930d050
> start commit:   8b787da7 Add linux-next specific files for 20201007
> git tree:   linux-next
> final oops: https://syzkaller.appspot.com/x/report.txt?x=116930d050
> console output: https://syzkaller.appspot.com/x/log.txt?x=166930d050
> kernel config:  https://syzkaller.appspot.com/x/.config?x=aac055e9c8fbd2b8
> dashboard link: https://syzkaller.appspot.com/bug?extid=fd15ff734dace9e16437
> syz repro:  https://syzkaller.appspot.com/x/repro.syz?x=119a056850
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=106c0a8b90
> 
> Reported-by: syzbot+fd15ff734dace9e16...@syzkaller.appspotmail.com
> Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in 
> fast path")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Ming, this looks like a call of percpu_ref_exit() on a zeroed refs (that
hasn't been initialized). Really a caller error imho, but might make sense
to be a bit safer there.

-- 
Jens Axboe

Re: general protection fault in percpu_ref_exit

2020-10-08 Thread syzbot 
syzbot has bisected this issue to:

commit 2b0d3d3e4fcfb19d10f9a82910b8f0f05c56ee3e
Author: Ming Lei 
Date:   Thu Oct 1 15:48:41 2020 +

percpu_ref: reduce memory footprint of percpu_ref in fast path

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=126930d050
start commit:   8b787da7 Add linux-next specific files for 20201007
git tree:   linux-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=116930d050
console output: https://syzkaller.appspot.com/x/log.txt?x=166930d050
kernel config:  https://syzkaller.appspot.com/x/.config?x=aac055e9c8fbd2b8
dashboard link: https://syzkaller.appspot.com/bug?extid=fd15ff734dace9e16437
syz repro:  https://syzkaller.appspot.com/x/repro.syz?x=119a056850
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=106c0a8b90

Reported-by: syzbot+fd15ff734dace9e16...@syzkaller.appspotmail.com
Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast 
path")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

general protection fault in percpu_ref_exit

2020-10-08 Thread syzbot 
Hello,

syzbot found the following issue on:

HEAD commit:8b787da7 Add linux-next specific files for 20201007
git tree:   linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15b6734f90
kernel config:  https://syzkaller.appspot.com/x/.config?x=aac055e9c8fbd2b8
dashboard link: https://syzkaller.appspot.com/bug?extid=fd15ff734dace9e16437
compiler:   gcc (GCC) 10.1.0-syz 20200507
syz repro:  https://syzkaller.appspot.com/x/repro.syz?x=119a056850
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=106c0a8b90

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fd15ff734dace9e16...@syzkaller.appspotmail.com

RDX: 0001 RSI: 2140 RDI: f501
RBP: 006dbc20 R08: 0001 R09: 
R10:  R11: 0246 R12: 006dbc2c
R13: 7ffe36a84a0f R14: 7f51c77e59c0 R15: 
general protection fault, probably for non-canonical address 
0xdc02:  [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0010-0x0017]
CPU: 1 PID: 6924 Comm: syz-executor821 Not tainted 
5.9.0-rc8-next-20201007-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 
01/01/2011
RIP: 0010:__percpu_ref_exit lib/percpu-refcount.c:112 [inline]
RIP: 0010:percpu_ref_exit+0x7f/0x210 lib/percpu-refcount.c:133
Code: e5 fc 48 89 ee e8 01 42 b9 fd 48 85 ed 74 60 e8 77 45 b9 fd 49 8d 7c 24 
10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 26 01 
00 00 49 83 7c 24 10 00 0f 85 01 01 00 00
RSP: 0018:c900054b7de0 EFLAGS: 00010202
RAX: dc00 RBX: 88802feb1658 RCX: 83bc130f
RDX: 0002 RSI: 83bc1319 RDI: 0010
RBP: 607f51875180 R08: 0001 R09: 88802feb1807
R10:  R11:  R12: 
R13: 88802feb1660 R14: 88802feb1800 R15: 88802feb1670
FS:  7f51c77e5700() GS:8880ae50() knlGS:
CS:  0010 DS:  ES:  CR0: 80050033
CR2: 2140 CR3: 12424000 CR4: 001506e0
DR0:  DR1:  DR2: 
DR3:  DR6: fffe0ff0 DR7: 0400
Call Trace:
 ioctx_alloc+0x2d2/0x1d60 fs/aio.c:804
 __do_sys_io_setup fs/aio.c:1326 [inline]
 __se_sys_io_setup fs/aio.c:1309 [inline]
 __x64_sys_io_setup+0xe9/0x230 fs/aio.c:1309
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x446769
Code: e8 bc b5 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 
ab 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:7f51c77e4db8 EFLAGS: 0246 ORIG_RAX: 00ce
RAX: ffda RBX: 006dbc28 RCX: 00446769
RDX: 0001 RSI: 2140 RDI: f501
RBP: 006dbc20 R08: 0001 R09: 
R10:  R11: 0246 R12: 006dbc2c
R13: 7ffe36a84a0f R14: 7f51c77e59c0 R15: 
Modules linked in:
---[ end trace 000c19ea8a5922ba ]---
RIP: 0010:__percpu_ref_exit lib/percpu-refcount.c:112 [inline]
RIP: 0010:percpu_ref_exit+0x7f/0x210 lib/percpu-refcount.c:133
Code: e5 fc 48 89 ee e8 01 42 b9 fd 48 85 ed 74 60 e8 77 45 b9 fd 49 8d 7c 24 
10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 26 01 
00 00 49 83 7c 24 10 00 0f 85 01 01 00 00
RSP: 0018:c900054b7de0 EFLAGS: 00010202
RAX: dc00 RBX: 88802feb1658 RCX: 83bc130f
RDX: 0002 RSI: 83bc1319 RDI: 0010
RBP: 607f51875180 R08: 0001 R09: 88802feb1807
R10:  R11:  R12: 
R13: 88802feb1660 R14: 88802feb1800 R15: 88802feb1670
FS:  7f51c77e5700() GS:8880ae50() knlGS:
CS:  0010 DS:  ES:  CR0: 80050033
CR2: 2140 CR3: 12424000 CR4: 001506e0
DR0:  DR1:  DR2: 
DR3:  DR6: fffe0ff0 DR7: 0400


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