general protection fault in do_move_mount (2)

syzbot
2019-06-18T10:47:13Z

Hello,

syzbot found the following crash on:

HEAD commit: 9e0babf2 Linux 5.2-rc5
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=138b310aa00000
kernel config: https://syzkaller.appspot.com/x/.config?x=d16883d6c7f0d717
dashboard link: https://syzkaller.appspot.com/bug?extid=6004acbaa1893ad013f0
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=154e8c2aa00000

The bug was bisected to:

commit 9c8ad7a2ff0bfe58f019ec0abc1fb965114dde7d
Author: David Howells <dhowells@redhat.com>
Date: Thu May 16 11:52:27 2019 +0000

uapi, x86: Fix the syscall numbering of the mount API syscalls [ver #2]

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14fa8411a00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=16fa8411a00000
console output: https://syzkaller.appspot.com/x/log.txt?x=12fa8411a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6004acbaa1893ad013f0@syzkaller.appspotmail.com
Fixes: 9c8ad7a2ff0b ("uapi, x86: Fix the syscall numbering of the mount API
syscalls [ver #2]")

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: 0 PID: 9133 Comm: syz-executor.0 Not tainted 5.2.0-rc5 #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:do_move_mount.isra.0+0x5fe/0xe10 fs/namespace.c:2602
Code: ff ff 00 0f 84 7a fb ff ff e8 de a4 b5 ff 48 8b 85 50 ff ff ff 48 8d
78 48 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f
85 6d 07 00 00 48 8b 85 50 ff ff ff 31 ff 4c 8b 78
RSP: 0018:ffff888097117d58 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff888097117ea8 RCX: 1ffff11015330137
RDX: 0000000000000006 RSI: ffffffff81bb1c82 RDI: 0000000000000032
RBP: ffff888097117e38 R08: ffff88808971c5c0 R09: ffffed1015d06be0
R10: ffffed1015d06bdf R11: ffff8880ae835efb R12: ffff88809f377f00
R13: ffff88821baa2420 R14: ffff888097117e90 R15: ffff8880a99809a0
FS: 00007f0eb2bcd700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa3553c2000 CR3: 00000000a8a61000 CR4: 00000000001406f0
Call Trace:
__do_sys_move_mount fs/namespace.c:3524 [inline]
__se_sys_move_mount fs/namespace.c:3483 [inline]
__x64_sys_move_mount+0x355/0x440 fs/namespace.c:3483
do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4592c9
Code: fd 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0eb2bccc78 EFLAGS: 00000246 ORIG_RAX: 00000000000001ad
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00000000004592c9
RDX: ffffffffffffff9c RSI: 0000000020000040 RDI: 0000000000000003
RBP: 000000000075c070 R08: 0000000000000066 R09: 0000000000000000
R10: 0000000020000100 R11: 0000000000000246 R12: 00007f0eb2bcd6d4
R13: 00000000004c5706 R14: 00000000004d9ba8 R15: 00000000ffffffff
Modules linked in:
---[ end trace 9c2a9754ccc962c7 ]---
RIP: 0010:do_move_mount.isra.0+0x5fe/0xe10 fs/namespace.c:2602
Code: ff ff 00 0f 84 7a fb ff ff e8 de a4 b5 ff 48 8b 85 50 ff ff ff 48 8d
78 48 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f
85 6d 07 00 00 48 8b 85 50 ff ff ff 31 ff 4c 8b 78
RSP: 0018:ffff888097117d58 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff888097117ea8 RCX: 1ffff11015330137
RDX: 0000000000000006 RSI: ffffffff81bb1c82 RDI: 0000000000000032
RBP: ffff888097117e38 R08: ffff88808971c5c0 R09: ffffed1015d06be0
R10: ffffed1015d06bdf R11: ffff8880ae835efb R12: ffff88809f377f00
R13: ffff88821baa2420 R14: ffff888097117e90 R15: ffff8880a99809a0
FS: 00007f0eb2bcd700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa3553c2000 CR3: 00000000a8a61000 CR4: 00000000001406f0

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