NetBSD Problem Report #56950

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Date: Wed,  3 Aug 2022 09:27:43 +0000 (UTC)
From: campbell+netbsd@mumble.net
Reply-To: campbell+netbsd@mumble.net
To: gnats-bugs@NetBSD.org
Subject: Race in vnode klist destruction?
X-Send-Pr-Version: www-1.0

>Number:         56950
>Category:       kern
>Synopsis:       Race in vnode klist destruction?
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    thorpej
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Aug 03 09:30:00 +0000 2022
>Closed-Date:    Sun Aug 20 06:57:04 +0000 2023
>Last-Modified:  Sun Aug 20 06:57:04 +0000 2023
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
La Fundacion NetBSD
>Environment:
hot like a greenhouse
>Description:
[ 158.8702193] panic: ASan: Unauthorized Access In 0xffffffff81ca635a: Addr 0xffffb1001400b418 [8 bytes, read, PoolUseAfterFree]

[ 158.8896562] cpu0: Begin traceback...
[ 158.9002072] vpanic() at netbsd:vpanic+0x282 sys/kern/subr_prf.c:293
[ 158.9402085] panic() at netbsd:panic+0x9e sys/kern/subr_prf.c:1043
[ 158.9702073] kasan_report() at netbsd:kasan_report+0x8f kasan_code_name sys/kern/subr_asan.c:168 [inline]
[ 158.9702073] kasan_report() at netbsd:kasan_report+0x8f sys/kern/subr_asan.c:200
[ 159.0002068] __asan_load8() at netbsd:__asan_load8+0xac kasan_shadow_8byte_isvalid sys/kern/subr_asan.c:370 [inline]
[ 159.0002068] __asan_load8() at netbsd:__asan_load8+0xac kasan_shadow_check sys/kern/subr_asan.c:420 [inline]
[ 159.0002068] __asan_load8() at netbsd:__asan_load8+0xac sys/kern/subr_asan.c:1207
[ 159.0302067] vcache_reclaim() at netbsd:vcache_reclaim+0x52b sys/kern/vfs_vnode.c:1923
[ 159.0702091] vrelel() at netbsd:vrelel+0x67a sys/kern/vfs_vnode.c:985
[ 159.1002077] vrele() at netbsd:vrele+0x51 sys/kern/vfs_vnode.c:1038
[ 159.1202065] layer_remove() at netbsd:layer_remove+0xa4 sys/miscfs/genfs/layer_vnops.c:631
[ 159.1502067] VOP_REMOVE() at netbsd:VOP_REMOVE+0x27c sys/kern/vnode_if.c:1219
[ 159.1802070] do_sys_unlinkat() at netbsd:do_sys_unlinkat+0x5b5 sys/kern/vfs_syscalls.c:2916
[ 159.2102077] syscall() at netbsd:syscall+0x25a sy_call sys/sys/syscallvar.h:65 [inline]
[ 159.2102077] syscall() at netbsd:syscall+0x25a sy_invoke sys/sys/syscallvar.h:94 [inline]
[ 159.2102077] syscall() at netbsd:syscall+0x25a sys/arch/x86/x86/syscall.c:138
[ 159.2215181] --- syscall (number 10) ---
[ 159.2327772] netbsd:syscall+0x25a:

Reported-by: syzbot+177e6808c863c4dd4584@syzkaller.appspotmail.com
https://syzkaller.appspot.com/bug?id=7ea755f80234f6a5c322864deba9b5abfc13c1b9
>How-To-Repeat:
syzbot did not find a reproducer.
>Fix:
Yes, please!

>Release-Note:

>Audit-Trail:

Responsible-Changed-From-To: kern-bug-people->thorpej
Responsible-Changed-By: thorpej@NetBSD.org
Responsible-Changed-When: Thu, 04 Aug 2022 03:26:49 +0000
Responsible-Changed-Why:
My bug.


State-Changed-From-To: open->analyzed
State-Changed-By: thorpej@NetBSD.org
State-Changed-When: Thu, 04 Aug 2022 03:26:49 +0000
State-Changed-Why:
Root cause analyzed.


State-Changed-From-To: analyzed->feedback
State-Changed-By: thorpej@NetBSD.org
State-Changed-When: Fri, 05 Aug 2022 05:21:56 +0000
State-Changed-Why:
Please confirm with vfs_vnode.c 1.145 and vnode.h 1.303.


From: "Jason R Thorpe" <thorpej@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/56950 CVS commit: src/sys
Date: Fri, 5 Aug 2022 05:20:39 +0000

 Module Name:	src
 Committed By:	thorpej
 Date:		Fri Aug  5 05:20:39 UTC 2022

 Modified Files:
 	src/sys/kern: vfs_vnode.c
 	src/sys/sys: vnode.h

 Log Message:
 In vcache_reclaim(), post NOTE_REVOKE immediately after changing the
 vnode state to VS_RECLAIMING, before we actually call VOP_RECLAIM(),
 which will release the reference on the lower node of a stacked FS
 vnode, which is likely to free the upper node's v_klist backing store.

 Acquire the vnode interlock when checking for kevent interest now,
 because the vp->v_klist pointer is now volatile.

 PR kern/56950


 To generate a diff of this commit:
 cvs rdiff -u -r1.144 -r1.145 src/sys/kern/vfs_vnode.c
 cvs rdiff -u -r1.302 -r1.303 src/sys/sys/vnode.h

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: feedback->closed
State-Changed-By: riastradh@NetBSD.org
State-Changed-When: Sun, 20 Aug 2023 06:57:04 +0000
State-Changed-Why:
no reproducer, syzbot has not found this again since last August
candidate fix committed, assuming fixed


>Unformatted:

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