Module Name: src
Committed By: riastradh
Date: Fri Jul 1 01:04:59 UTC 2022
Modified Files:
src/sys/dev: sequencer.c
Log Message:
sequencer(4): Fix lock leak in ioctl(FIOASYNC).
Reported-by: syzbot+0bfe9054ab0e70ab0...@syzkaller.appspotmail.com
Reported-by: syzbot+f2c5459483e60dd2c...@syzkaller.appspotmail.com
Reported-by: syzbot+d932ddf0ec7e30784...@syzkaller.appspotmail.com
Note: The evidence from
https://syzkaller.appspot.com/bug?id=19e1c8779bb0e020188ca80a586e470b59d7525d
suggests in the stack trace that the syscall was 16, which is chown.
This is not accurate; it happens because the x86 syscall logic sets
rax in the trapframe to the return value (in this case, 16 is EBUSY)
_before_ calling userret which does the lockdebug checks, and ddb
uses the trapframe's rax to show what the syscall number was when
printing its stack trace:
[ 104.0605877] Mutex error: lwp_exit,1084: sleep lock held
[ 104.0605877] lock address : 0xffffd9801269e050 type : sleep/adaptive
...
[ 104.5005727] syscall() at netbsd:syscall+0x323 sys/arch/x86/x86/syscall.c:92
[ 104.5115909] --- syscall (number 16) ---
XXX Maybe we should record the syscall number elsewhere so this is
not so confusing -- second time in 24h I've been bitten by this, and
in a different way.
To generate a diff of this commit:
cvs rdiff -u -r1.80 -r1.81 src/sys/dev/sequencer.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/sequencer.c
diff -u src/sys/dev/sequencer.c:1.80 src/sys/dev/sequencer.c:1.81
--- src/sys/dev/sequencer.c:1.80 Sat Jun 4 03:31:10 2022
+++ src/sys/dev/sequencer.c Fri Jul 1 01:04:59 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: sequencer.c,v 1.80 2022/06/04 03:31:10 pgoyette Exp $ */
+/* $NetBSD: sequencer.c,v 1.81 2022/07/01 01:04:59 riastradh Exp $ */
/*
* Copyright (c) 1998, 2008 The NetBSD Foundation, Inc.
@@ -55,7 +55,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sequencer.c,v 1.80 2022/06/04 03:31:10 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sequencer.c,v 1.81 2022/07/01 01:04:59 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "midi.h"
@@ -744,8 +744,10 @@ sequencerioctl(dev_t dev, u_long cmd, vo
case FIOASYNC:
if (*(int *)addr) {
- if (sc->async != 0)
- return EBUSY;
+ if (sc->async != 0) {
+ error = EBUSY;
+ break;
+ }
sc->async = curproc->p_pid;
DPRINTF(("%s: FIOASYNC %d\n", __func__,
sc->async));
