Re: [syzbot] [btrfs?] kernel BUG in clear_inode

[Julian Sun <sunjunchao2870@gmail.com>]

On Thu, 2024-06-06 at 22:05 -0700, syzbot wrote:

#syz test: upstream d30d0e49da71

diff --git a/fs/inode.c b/fs/inode.c
index 3a41f83a4ba5..011f630777d0 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -723,6 +723,10 @@ void evict_inodes(struct super_block *sb)
                        continue;
 
                spin_lock(&inode->i_lock);
+               if (atomic_read(&inode->i_count)) {
+                       spin_unlock(&inode->i_lock);
+                       continue;
+               }
                if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE))
{
                        spin_unlock(&inode->i_lock);
                        continue;

> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    d30d0e49da71 Merge tag 'net-6.10-rc3' of
> git://git.kernel...
> git tree:       upstream
> console output:
> https://syzkaller.appspot.com/x/log.txt?x=1736820a980000
> kernel config: 
> https://syzkaller.appspot.com/x/.config?x=399230c250e8119c
> dashboard link:
> https://syzkaller.appspot.com/bug?extid=67ba3c42bcbb4665d3ad
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils
> for Debian) 2.40
> syz repro:     
> https://syzkaller.appspot.com/x/repro.syz?x=11a9aa22980000
> C reproducer:  
> https://syzkaller.appspot.com/x/repro.c?x=14c57f16980000
> 
> Downloadable assets:
> disk image (non-bootable):
> https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-d30d0e49.raw.xz
> vmlinux:
> https://storage.googleapis.com/syzbot-assets/f1276023ed77/vmlinux-d30d0e49.xz
> kernel image:
> https://storage.googleapis.com/syzbot-assets/a33f372d4fb8/bzImage-d30d0e49.xz
> mounted in repro:
> https://storage.googleapis.com/syzbot-assets/7fc863ff127d/mount_0.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the
> commit:
> Reported-by: syzbot+67ba3c42bcbb4665d3ad@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> kernel BUG at fs/inode.c:626!
> Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
> CPU: 1 PID: 5273 Comm: syz-executor331 Not tainted 6.10.0-rc2-
> syzkaller-00222-gd30d0e49da71 #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-
> debian-1.16.2-1 04/01/2014
> RIP: 0010:clear_inode+0x15b/0x190 fs/inode.c:626
> Code: 00 00 00 5b 5d 41 5c c3 cc cc cc cc e8 5e c1 8c ff 90 0f 0b e8
> 56 c1 8c ff 90 0f 0b e8 4e c1 8c ff 90 0f 0b e8 46 c1 8c ff 90 <0f>
> 0b e8 3e c1 8c ff 90 0f 0b e8 e6 92 e8 ff e9 d2 fe ff ff e8 dc
> RSP: 0018:ffffc900036f7ac0 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff888030369e90 RCX: ffffffff82012340
> RDX: ffff888024190000 RSI: ffffffff820123aa RDI: 0000000000000007
> RBP: 0000000000000040 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000040 R11: 0000000000000001 R12: 0000000000000020
> R13: ffff88802f942000 R14: 0000000000000000 R15: ffff888030369e90
> FS:  000055556268d380(0000) GS:ffff88806b100000(0000)
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000555562697708 CR3: 000000001e888000 CR4: 0000000000350ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  btrfs_evict_inode+0x529/0xe80 fs/btrfs/inode.c:5262
>  evict+0x2ed/0x6c0 fs/inode.c:667
>  dispose_list+0x117/0x1e0 fs/inode.c:700
>  evict_inodes+0x34e/0x450 fs/inode.c:750
>  generic_shutdown_super+0xb5/0x3d0 fs/super.c:627
>  kill_anon_super+0x3a/0x60 fs/super.c:1226
>  btrfs_kill_super+0x3b/0x50 fs/btrfs/super.c:2096
>  deactivate_locked_super+0xbe/0x1a0 fs/super.c:473
>  deactivate_super+0xde/0x100 fs/super.c:506
>  cleanup_mnt+0x222/0x450 fs/namespace.c:1267
>  task_work_run+0x14e/0x250 kernel/task_work.c:180
>  resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
>  exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
>  syscall_exit_to_user_mode+0x278/0x2a0 kernel/entry/common.c:218
>  do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f2ba3059777
> Code: 07 00 48 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 c3 66
> 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48>
> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8
> RSP: 002b:00007fff42f9ee78 EFLAGS: 00000206 ORIG_RAX:
> 00000000000000a6
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f2ba3059777
> RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007fff42f9ef30
> RBP: 00007fff42f9ef30 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000ffffffff R11: 0000000000000206 R12: 00007fff42f9ffa0
> R13: 000055556268f6d0 R14: 431bde82d7b634db R15: 00007fff42f9ffc0
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:clear_inode+0x15b/0x190 fs/inode.c:626
> Code: 00 00 00 5b 5d 41 5c c3 cc cc cc cc e8 5e c1 8c ff 90 0f 0b e8
> 56 c1 8c ff 90 0f 0b e8 4e c1 8c ff 90 0f 0b e8 46 c1 8c ff 90 <0f>
> 0b e8 3e c1 8c ff 90 0f 0b e8 e6 92 e8 ff e9 d2 fe ff ff e8 dc
> RSP: 0018:ffffc900036f7ac0 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff888030369e90 RCX: ffffffff82012340
> RDX: ffff888024190000 RSI: ffffffff820123aa RDI: 0000000000000007
> RBP: 0000000000000040 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000040 R11: 0000000000000001 R12: 0000000000000020
> R13: ffff88802f942000 R14: 0000000000000000 R15: ffff888030369e90
> FS:  000055556268d380(0000) GS:ffff88806b100000(0000)
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000555562697708 CR3: 000000001e888000 CR4: 0000000000350ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before
> testing.

-- 
Julian Sun <sunjunchao2870@gmail.com>