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

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 90 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 1 PID: 90 Comm: kworker/u32:4 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
Workqueue: events_unbound netfs_write_collection_worker
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:ffffc9000163f830 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff814ff319
RDX: ffff88801c180000 RSI: ffffffff814ff326 RDI: 0000000000000001
RBP: ffff8880127f4bb8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000002 R12: ffff8880127f4bb0
R13: ffff8880127f4bb8 R14: ffff88802ad24400 R15: 00000000ffffffea
FS:  0000000000000000(0000) GS:ffff88806b100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001000 CR3: 000000002c226000 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_client_rpc+0x591/0xc10 net/9p/client.c:759
 p9_client_clunk+0x93/0x170 net/9p/client.c:1450
 p9_fid_put include/net/9p/client.h:280 [inline]
 v9fs_free_request+0xdc/0x110 fs/9p/vfs_addr.c:138
 netfs_free_request+0x22c/0x690 fs/netfs/objects.c:133
 netfs_put_request+0x19b/0x1f0 fs/netfs/objects.c:165
 netfs_write_collection_worker+0x19d0/0x59e0 fs/netfs/write_collect.c:701
 process_one_work+0x9fb/0x1b60 kernel/workqueue.c:3231
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xf70 kernel/workqueue.c:3393
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </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=16c7da34980000
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=1097adf0980000