From f07d228794be5451d39ef906154838d287fb4576 Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Fri, 14 Oct 2022 14:32:48 +0800 Subject: [PATCH] ALSA: pcm: oss: Fix race at SNDCTL_DSP_SYNC stable inclusion from stable-v5.4.215 commit 4051324a6dafd7053c74c475e80b3ba10ae672b0 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5T9C3 CVE: CVE-2022-3303 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs?h=v6.0-rc5&id=8423f0b6d513b259fdab9c9bf4aaa6188d054c2d --------------------------- [ Upstream commit 8423f0b6d513b259fdab9c9bf4aaa6188d054c2d ] There is a small race window at snd_pcm_oss_sync() that is called from OSS PCM SNDCTL_DSP_SYNC ioctl; namely the function calls snd_pcm_oss_make_ready() at first, then takes the params_lock mutex for the rest. When the stream is set up again by another thread between them, it leads to inconsistency, and may result in unexpected results such as NULL dereference of OSS buffer as a fuzzer spotted recently. The fix is simply to cover snd_pcm_oss_make_ready() call into the same params_lock mutex with snd_pcm_oss_make_ready_locked() variant. Reported-and-tested-by: butt3rflyh4ck Reviewed-by: Jaroslav Kysela Cc: Link: https://lore.kernel.org/r/CAFcO6XN7JDM4xSXGhtusQfS2mSBcx50VJKwQpCq=WeLt57aaZA@mail.gmail.com Link: https://lore.kernel.org/r/20220905060714.22549-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin Signed-off-by: Xia Longlong Reviewed-by: Kefeng Wang Signed-off-by: Zheng Zengkai --- sound/core/oss/pcm_oss.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c index f88de74da1eb..de6f94bee50b 100644 --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -1662,13 +1662,14 @@ static int snd_pcm_oss_sync(struct snd_pcm_oss_file *pcm_oss_file) runtime = substream->runtime; if (atomic_read(&substream->mmap_count)) goto __direct; - if ((err = snd_pcm_oss_make_ready(substream)) < 0) - return err; atomic_inc(&runtime->oss.rw_ref); if (mutex_lock_interruptible(&runtime->oss.params_lock)) { atomic_dec(&runtime->oss.rw_ref); return -ERESTARTSYS; } + err = snd_pcm_oss_make_ready_locked(substream); + if (err < 0) + goto unlock; format = snd_pcm_oss_format_from(runtime->oss.format); width = snd_pcm_format_physical_width(format); if (runtime->oss.buffer_used > 0) { -- GitLab