syzbot


WARNING: refcount bug in p9_req_put (3)

Status: upstream: reported C repro on 2024/01/26 09:05
Subsystems: v9fs
[Documentation on labels]
Reported-by: syzbot+d99d2414db66171fccbb@syzkaller.appspotmail.com
First crash: 461d, last: 5d17h
Discussions (6)
Title Replies (including bot) Last reply
[syzbot] Monthly v9fs report (Apr 2025) 0 (1) 2025/04/14 10:17
[syzbot] Monthly v9fs report (Mar 2025) 0 (1) 2025/03/04 15:15
[syzbot] Monthly v9fs report (Jan 2025) 0 (1) 2025/01/02 13:21
[syzbot] Monthly v9fs report (Aug 2024) 0 (1) 2024/08/29 13:20
[syzbot] [net?] [v9fs?] WARNING: refcount bug in p9_req_put (3) 2 (4) 2024/07/22 06:14
[syzbot] Monthly v9fs report (Apr 2024) 0 (1) 2024/04/30 07:12
Similar bugs (3)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 WARNING: refcount bug in p9_req_put 2 2004d 2045d 0/1 auto-closed as invalid on 2020/02/28 21:29
upstream WARNING: refcount bug in p9_req_put v9fs syz inconclusive done 6 1801d 2354d 15/28 fixed on 2020/11/16 12:12
upstream WARNING: refcount bug in p9_req_put (2) v9fs 9 604d 950d 0/28 auto-obsoleted due to no activity on 2023/12/09 05:29
Last patch testing requests (3)
Created Duration User Patch Repo Result
2025/01/24 14:02 11m retest repro upstream error
2024/11/24 01:46 29m retest repro upstream OK log
2024/09/23 13:53 19m retest repro upstream OK log

Sample crash report:
9p: Unknown Cache mode or invalid value fs
9pnet: Tag 65535 still in use
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 2 PID: 6261 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 2 UID: 0 PID: 6261 Comm: syz.2.58 Not tainted 6.15.0-rc1-syzkaller-00246-g900241a5cc15 #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 08 ab eb fc 84 db 0f 85 66 ff ff ff e8 1b b0 eb fc c6 05 5e 26 9f 0b 01 90 48 c7 c7 40 0f f4 8b e8 f7 40 ab fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 f8 af eb fc 0f b6 1d 39 26 9f 0b 31
RSP: 0018:ffffc900033479e0 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817acff8
RDX: ffff88802d434880 RSI: ffffffff817ad005 RDI: 0000000000000001
RBP: ffff88802814aaa8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88802814aaa8
R13: ffff88802ef29000 R14: dffffc0000000000 R15: 1ffff92000668f47
FS:  00007f53b8b516c0(0000) GS:ffff8880d6bb3000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001000 CR3: 0000000036166000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 p9_req_put+0x1ec/0x250 net/9p/client.c:404
 p9_tag_cleanup net/9p/client.c:431 [inline]
 p9_client_destroy+0x22b/0x480 net/9p/client.c:1086
 v9fs_session_init+0xbab/0x1a80 fs/9p/v9fs.c:490
 v9fs_mount+0xc5/0xa30 fs/9p/vfs_super.c:122
 legacy_get_tree+0x109/0x220 fs/fs_context.c:662
 vfs_get_tree+0x8b/0x340 fs/super.c:1759
 do_new_mount fs/namespace.c:3879 [inline]
 path_mount+0x14d4/0x1f30 fs/namespace.c:4206
 do_mount fs/namespace.c:4219 [inline]
 __do_sys_mount fs/namespace.c:4430 [inline]
 __se_sys_mount fs/namespace.c:4407 [inline]
 __x64_sys_mount+0x28d/0x310 fs/namespace.c:4407
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f53b7d8d169
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f53b8b51038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f53b7fa5fa0 RCX: 00007f53b7d8d169
RDX: 00002000000004c0 RSI: 0000200000000480 RDI: 00002000000001c0
RBP: 00007f53b7e0e990 R08: 0000200000000840 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f53b7fa5fa0 R15: 00007ffc0d133e78
 </TASK>

Crashes (50):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/04/11 18:22 upstream 900241a5cc15 12ba9c21 .config console log report syz / log [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/03/21 15:04 upstream b3ee1e460951 62330552 .config console log report syz / log [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/12/20 16:15 upstream 8faabc041a00 49cfeac8 .config console log report syz / log [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/04/21 04:47 upstream 6fea5fabd332 2a20f901 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/04/11 17:06 upstream 900241a5cc15 12ba9c21 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/04/05 10:03 upstream 9f867ba24d36 c53ea9c9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/03/21 14:26 upstream b3ee1e460951 62330552 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/03/07 05:51 upstream f315296c92fd 831e3629 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/02/24 13:44 upstream d082ecbc71e9 d34966d1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/02/21 05:22 upstream e9a8cac0bf89 0808a665 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/02/19 12:47 upstream 6537cfb395f3 cbd8edab .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/02/18 15:50 upstream 2408a807bfc3 c37c7249 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/02/17 13:42 upstream 0ad2507d5d93 9be4ace3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/02/17 03:14 upstream ba643b6d8440 40a34ec9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/02/10 12:24 upstream a64dcfb451e2 43f51a00 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/01/10 13:55 upstream 2144da25584e 67d7ec0a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/01/06 17:25 upstream 5428dc1906dd f3558dbf .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/01/01 14:54 upstream ccb98ccef0e5 d3ccff63 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/12/20 10:59 upstream 8faabc041a00 49cfeac8 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/12/16 07:38 upstream dccbe2047a5b 7cbfbb3a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/11/10 01:22 upstream da4373fbcf00 6b856513 .config console log report syz / log [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/11/09 22:02 upstream da4373fbcf00 6b856513 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/09/09 13:41 upstream da3ea35007d0 8f722c94 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/08/02 22:09 upstream 948752d2e010 53683cf2 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/08/02 22:09 upstream 948752d2e010 53683cf2 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/07/31 12:35 upstream c91a7dee0555 6fde257d .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/07/31 12:29 upstream c91a7dee0555 6fde257d .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/07/22 06:13 upstream 7846b618e0a4 b88348e9 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/07/22 04:03 upstream 7846b618e0a4 b88348e9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/05/15 16:45 upstream 1b294a1f3561 7e8e0c0f .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/04/15 09:24 upstream 72374d71c315 c8349e48 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/04/15 09:24 upstream 72374d71c315 c8349e48 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2024/03/02 16:41 upstream 5ad3cb0ed525 25905f5d .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in p9_req_put
2025/03/24 08:23 upstream 586de92313fc 875573af .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2025/03/11 11:26 upstream 4d872d51bc9d 16256247 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2025/02/26 01:19 upstream 2a1944bff549 d34966d1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2025/02/18 10:10 upstream 2408a807bfc3 c37c7249 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2025/02/05 05:23 upstream 5c8c229261f1 5896748e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2025/02/05 05:19 upstream 5c8c229261f1 5896748e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2025/02/05 05:19 upstream 5c8c229261f1 5896748e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2025/01/06 15:22 upstream 5428dc1906dd f3558dbf .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2024/08/31 21:58 upstream 1934261d8974 1eda0d14 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2024/08/28 00:16 upstream 3ec3f5fc4a91 a1a7b2f0 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2024/08/15 15:32 upstream 1fb918967b56 e4bacdaf .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2024/08/01 21:05 upstream c0ecd6388360 1e9c4cf3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2024/05/21 06:14 upstream 6e51b4b5bbc0 c2e07261 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2024/04/21 01:47 upstream 977b1ef51866 af24b050 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2024/01/27 14:27 upstream 3a5879d495b2 cc4a4020 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
2024/01/21 21:11 upstream 4fbbed787267 9bd8dcda .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in p9_req_put
* Struck through repros no longer work on HEAD.