Re: [syzbot] [v9fs?] KASAN: slab-use-after-free Read in p9_fid_destroy

[syzbot <syzbot+d7c7a495a5e466c031b6@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: refcount bug in p9_req_put

9pnet: Found fid 3 not clunked
9pnet: Tag 0 still in use
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 3 PID: 5345 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 3 PID: 5345 Comm: syz-executor.3 Not tainted 6.9.0-syzkaller-08284-gea5f6ad9ad96-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 98 2d 0d fd 84 db 0f 85 66 ff ff ff e8 0b 33 0d fd c6 05 97 cc 4c 0b 01 90 48 c7 c7 00 24 8f 8b e8 f7 47 cf fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 e8 32 0d fd 0f b6 1d 72 cc 4c 0b 31
RSP: 0018:ffffc900037bfc78 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff814ff319
RDX: ffff88801f798000 RSI: ffffffff814ff326 RDI: 0000000000000001
RBP: ffff88802c045108 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff88802b369870
R13: ffff88802c045108 R14: ffff88802b369800 R15: ffff888025704c80
FS:  000055556f75f480(0000) GS:ffff88806b300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555569357788 CR3: 00000000278a4000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:275 [inline]
 __refcount_dec_and_test include/linux/refcount.h:307 [inline]
 refcount_dec_and_test include/linux/refcount.h:325 [inline]
 p9_req_put+0x1f4/0x250 net/9p/client.c:402
 p9_tag_cleanup net/9p/client.c:429 [inline]
 p9_client_destroy+0x219/0x540 net/9p/client.c:1077
 v9fs_session_close+0x49/0x2d0 fs/9p/v9fs.c:506
 v9fs_kill_super+0x4d/0xa0 fs/9p/vfs_super.c:196
 deactivate_locked_super+0xbe/0x1a0 fs/super.c:472
 deactivate_super+0xde/0x100 fs/super.c:505
 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+0xdc/0x260 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f936f47e217
Code: b0 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 b0 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffeefbb92f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f936f47e217
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffeefbb93b0
RBP: 00007ffeefbb93b0 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffeefbba470
R13: 00007f936f4c8336 R14: 000000000001951c R15: 0000000000000005
 </TASK>


Tested on:

commit:         ea5f6ad9 Merge tag 'platform-drivers-x86-v6.10-1' of g..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=14b71442980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f1cd4092753f97c5
dashboard link: https://syzkaller.appspot.com/bug?extid=d7c7a495a5e466c031b6
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=160f3b68980000