On 4/1/21 9:45 AM, Christian Brauner wrote: > On Thu, Apr 01, 2021 at 02:09:20AM -0700, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: d19cc4bf Merge tag 'trace-v5.12-rc5' of git://git.kernel.o.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=1018f281d00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=d1a3d65a48dbd1bc >> dashboard link: https://syzkaller.appspot.com/bug?extid=c88a7030da47945a3cc3 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12f50d11d00000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=137694a1d00000 >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+c88a7030da47945a3cc3@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> ------------[ cut here ]------------ >> WARNING: CPU: 1 PID: 8409 at fs/namespace.c:1186 mntput_no_expire+0xaca/0xcb0 fs/namespace.c:1186 >> Modules linked in: >> CPU: 1 PID: 8409 Comm: syz-executor035 Not tainted 5.12.0-rc5-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> RIP: 0010:mntput_no_expire+0xaca/0xcb0 fs/namespace.c:1186 >> Code: ff 48 c7 c2 e0 cb 78 89 be c2 02 00 00 48 c7 c7 a0 cb 78 89 c6 05 e5 6d e5 0b 01 e8 ff e1 f6 06 e9 3f fd ff ff e8 c6 a5 a8 ff <0f> 0b e9 fc fc ff ff e8 ba a5 a8 ff e8 55 dc 94 ff 31 ff 89 c5 89 >> RSP: 0018:ffffc9000165fc78 EFLAGS: 00010293 >> RAX: 0000000000000000 RBX: 1ffff920002cbf95 RCX: 0000000000000000 >> RDX: ffff88802072d4c0 RSI: ffffffff81cb4b8a RDI: 0000000000000003 >> RBP: ffff888011656900 R08: 0000000000000000 R09: ffffffff8fa978af >> R10: ffffffff81cb4884 R11: 0000000000000000 R12: 0000000000000008 >> R13: ffffc9000165fcc8 R14: dffffc0000000000 R15: 00000000ffffffff >> FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 000055a722053160 CR3: 000000000bc8e000 CR4: 00000000001506e0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Call Trace: >> mntput fs/namespace.c:1232 [inline] >> cleanup_mnt+0x523/0x530 fs/namespace.c:1132 >> task_work_run+0xdd/0x1a0 kernel/task_work.c:140 >> exit_task_work include/linux/task_work.h:30 [inline] >> do_exit+0xbfc/0x2a60 kernel/exit.c:825 >> do_group_exit+0x125/0x310 kernel/exit.c:922 >> __do_sys_exit_group kernel/exit.c:933 [inline] >> __se_sys_exit_group kernel/exit.c:931 [inline] >> __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931 >> do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> RIP: 0033:0x446af9 >> Code: Unable to access opcode bytes at RIP 0x446acf. >> RSP: 002b:00000000005dfe48 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 >> RAX: ffffffffffffffda RBX: 00000000004ce450 RCX: 0000000000446af9 >> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000001 >> RBP: 0000000000000001 R08: ffffffffffffffbc R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004ce450 >> R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001 > > [+Cc Jens + io_uring] > > Hm, this reproducer uses io_uring and it's the io_uring_enter() that > triggers this reliably. With this reproducer I've managed to reproduce > the issue on v5.12-rc4, and v5.12-rc3, v5.12-rc2 and v5.12-rc1. > It's not reproducible at > 9820b4dca0f9c6b7ab8b4307286cdace171b724d > which is the commit immediately before the first v5.12 io_uring merge. > It's first reproducible with the first io_uring merge for v5.12, i.e. > 5bbb336ba75d95611a7b9456355b48705016bdb1 Thanks, that's good info. I'll take a look at it and see if I can reproduce. -- Jens Axboe
