Re: general protection fault in get_task_pid

[Christian Brauner <christian@brauner.io>]

On Mon, Jul 01, 2019 at 06:17:06AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    556e2f60 Merge tag 'clk-fixes-for-linus' of git://git.kern..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=112a45a9a00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9a31528e58cc12e2
> dashboard link: https://syzkaller.appspot.com/bug?extid=002e636502bc4b64eb5c
> compiler:       clang version 9.0.0 (/home/glider/llvm/clang
> 80fee25776c2fb61e74c1ecb1a523375c2500b69)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1716d35ba00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1489f565a00000
> 
> The bug was bisected to:
> 
> commit 6fd2fe494b17bf2dec37b610d23a43a72b16923a
> Author: Al Viro <viro@zeniv.linux.org.uk>
> Date:   Thu Jun 27 02:22:09 2019 +0000
> 
>     copy_process(): don't use ksys_close() on cleanups

I think I see the issue. Will hopefully have a fix in a bit.

> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=135a66f9a00000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=10da66f9a00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=175a66f9a00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+002e636502bc4b64eb5c@syzkaller.appspotmail.com
> Fixes: 6fd2fe494b17 ("copy_process(): don't use ksys_close() on cleanups")
> 
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
> R13: 00007ffc15fbb0ff R14: 00007ff07e47e9c0 R15: 0000000000000000
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 7990 Comm: syz-executor290 Not tainted 5.2.0-rc6+ #9
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:__read_once_size include/linux/compiler.h:194 [inline]
> RIP: 0010:get_task_pid+0xe1/0x210 kernel/pid.c:372
> Code: 89 ff e8 62 27 5f 00 49 8b 07 44 89 f1 4c 8d bc c8 90 01 00 00 eb 0c
> e8 0d fe 25 00 49 81 c7 38 05 00 00 4c 89 f8 48 c1 e8 03 <80> 3c 18 00 74 08
> 4c 89 ff e8 31 27 5f 00 4d 8b 37 e8 f9 47 12 00
> RSP: 0018:ffff88808a4a7d78 EFLAGS: 00010203
> RAX: 00000000000000a7 RBX: dffffc0000000000 RCX: ffff888088180600
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff88808a4a7d90 R08: ffffffff814fb3a8 R09: ffffed1015d66bf8
> R10: ffffed1015d66bf8 R11: 1ffff11015d66bf7 R12: 0000000000041ffc
> R13: 1ffff11011494fbc R14: 0000000000000000 R15: 000000000000053d
> FS:  00007ff07e47e700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000004b5100 CR3: 0000000094df2000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  _do_fork+0x1b9/0x5f0 kernel/fork.c:2360
>  __do_sys_clone kernel/fork.c:2454 [inline]
>  __se_sys_clone kernel/fork.c:2448 [inline]
>  __x64_sys_clone+0xc1/0xd0 kernel/fork.c:2448
>  do_syscall_64+0xfe/0x140 arch/x86/entry/common.c:301
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x446649
> 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 2b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ff07e47ddb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
> RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 0000000000446649
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000041ffc
> RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
> R13: 00007ffc15fbb0ff R14: 00007ff07e47e9c0 R15: 0000000000000000
> Modules linked in:
> ---[ end trace 403a74d6aeda7e67 ]---
> RIP: 0010:__read_once_size include/linux/compiler.h:194 [inline]
> RIP: 0010:get_task_pid+0xe1/0x210 kernel/pid.c:372
> Code: 89 ff e8 62 27 5f 00 49 8b 07 44 89 f1 4c 8d bc c8 90 01 00 00 eb 0c
> e8 0d fe 25 00 49 81 c7 38 05 00 00 4c 89 f8 48 c1 e8 03 <80> 3c 18 00 74 08
> 4c 89 ff e8 31 27 5f 00 4d 8b 37 e8 f9 47 12 00
> RSP: 0018:ffff88808a4a7d78 EFLAGS: 00010203
> RAX: 00000000000000a7 RBX: dffffc0000000000 RCX: ffff888088180600
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff88808a4a7d90 R08: ffffffff814fb3a8 R09: ffffed1015d66bf8
> R10: ffffed1015d66bf8 R11: 1ffff11015d66bf7 R12: 0000000000041ffc
> R13: 1ffff11011494fbc R14: 0000000000000000 R15: 000000000000053d
> FS:  00007ff07e47e700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000004b5100 CR3: 0000000094df2000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
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