The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=62c4afcb460457bae055d756b24d5b5e5535903c
commit 62c4afcb460457bae055d756b24d5b5e5535903c Author: Mark Johnston <[email protected]> AuthorDate: 2026-08-24 15:20:32 +0000 Commit: Mark Johnston <[email protected]> CommitDate: 2026-08-25 15:46:24 +0000 dsp: Fix a potential use-after-free in dsp_oss_syncstart() This function has a loop where it attempts to lock all channels in a group. If doing so would block, it releases all locks, sleeps for a bit, and tries again. However, once the syncgroup lock is dropped, nothing prevents the syncgroup structure from being freed. Fix the inner loop: after waking up, break out of it unconditionally and start everything again. I think the old code was also buggy and not well-exercised: after waking up we'd continue to try and continue locking channels. Then we'd try again from the beginning and fail to lock the channels we had already locked. Approved by: so Security: FreeBSD-SA-26:58.sound Security: CVE-2026-58091 Reported by: Hazley Samsudin of GovTech CSG Reviewed by: christos Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D58912 --- sys/dev/sound/pcm/channel.h | 9 +++++---- sys/dev/sound/pcm/dsp.c | 17 ++++++----------- 2 files changed, 11 insertions(+), 15 deletions(-) diff --git a/sys/dev/sound/pcm/channel.h b/sys/dev/sound/pcm/channel.h index aac6ab368625..2f71f0708c8e 100644 --- a/sys/dev/sound/pcm/channel.h +++ b/sys/dev/sound/pcm/channel.h @@ -57,10 +57,11 @@ struct pcmchan_syncmember; extern struct mtx snd_pcm_syncgroups_mtx; extern SLIST_HEAD(pcm_synclist, pcmchan_syncgroup) snd_pcm_syncgroups; -#define PCM_SG_LOCK() mtx_lock(&snd_pcm_syncgroups_mtx) -#define PCM_SG_TRYLOCK() mtx_trylock(&snd_pcm_syncgroups_mtx) -#define PCM_SG_UNLOCK() mtx_unlock(&snd_pcm_syncgroups_mtx) -#define PCM_SG_LOCKASSERT(arg) mtx_assert(&snd_pcm_syncgroups_mtx, arg) +#define PCM_SG_LOCKPTR() (&snd_pcm_syncgroups_mtx) +#define PCM_SG_LOCK() mtx_lock(PCM_SG_LOCKPTR()) +#define PCM_SG_TRYLOCK() mtx_trylock(PCM_SG_LOCKPTR()) +#define PCM_SG_UNLOCK() mtx_unlock(PCM_SG_LOCKPTR()) +#define PCM_SG_LOCKASSERT(arg) mtx_assert(PCM_SG_LOCKPTR(), arg) /** * @brief Specifies an audio device sync group diff --git a/sys/dev/sound/pcm/dsp.c b/sys/dev/sound/pcm/dsp.c index 18d679c81433..c92c55b02cff 100644 --- a/sys/dev/sound/pcm/dsp.c +++ b/sys/dev/sound/pcm/dsp.c @@ -2684,14 +2684,11 @@ dsp_oss_syncstart(int sg_id) struct pcmchan_syncmember *sm, *sm_tmp; struct pcmchan_syncgroup *sg; struct pcm_channel *c; - int ret, needlocks; + int ret; - /* Get the synclists lock */ PCM_SG_LOCK(); - do { ret = 0; - needlocks = 0; /* Search for syncgroup by ID */ SLIST_FOREACH(sg, &snd_pcm_syncgroups, link) { @@ -2728,16 +2725,14 @@ dsp_oss_syncstart(int sg_id) } /** @todo Is PRIBIO correct/ */ - ret = msleep(sm, &snd_pcm_syncgroups_mtx, + ret = msleep(sm, PCM_SG_LOCKPTR(), PRIBIO | PCATCH, "pcmsg", timo); - if (ret == EINTR || ret == ERESTART) - break; - - needlocks = 1; - ret = 0; /* Assumes ret == EAGAIN... */ + if (ret == EAGAIN) + ret = 0; + break; } } - } while (needlocks && ret == 0); + } while (ret == 0 && sm != NULL); /* Proceed only if no errors encountered. */ if (ret == 0) {
