lkml.org 
[lkml]   [2022]   [Oct]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.10 10/54] ALSA: pcm: oss: Fix race at SNDCTL_DSP_SYNC
    Date
    From: Takashi Iwai <tiwai@suse.de>

    commit 8423f0b6d513b259fdab9c9bf4aaa6188d054c2d upstream.

    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 <butterflyhuangxx@gmail.com>
    Reviewed-by: Jaroslav Kysela <perex@perex.cz>
    Cc: <stable@vger.kernel.org>
    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 <tiwai@suse.de>
    Signed-off-by: Zubin Mithra <zsm@google.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    sound/core/oss/pcm_oss.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    --- 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_p
    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) {

    \
     
     \ /
      Last update: 2022-10-13 19:57    [W:2.872 / U:0.280 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site