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    Subject[PATCH 4.19 274/346] ALSA: pcm: oss: Fix a few more UBSAN fixes
    Date
    From: Takashi Iwai <tiwai@suse.de>

    commit 11cb881bf075cea41092a20236ba708b18e1dbb2 upstream.

    There are a few places that call round{up|down}_pow_of_two() with the
    value zero, and this causes undefined behavior warnings. Avoid
    calling those macros if such a nonsense value is passed; it's a minor
    optimization as well, as we handle it as either an error or a value to
    be skipped, instead.

    Reported-by: syzbot+33ef0b6639a8d2d42b4c@syzkaller.appspotmail.com
    Cc: <stable@vger.kernel.org>
    Link: https://lore.kernel.org/r/20201218161730.26596-1-tiwai@suse.de
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    sound/core/oss/pcm_oss.c | 22 ++++++++++++++--------
    1 file changed, 14 insertions(+), 8 deletions(-)

    --- a/sound/core/oss/pcm_oss.c
    +++ b/sound/core/oss/pcm_oss.c
    @@ -708,6 +708,8 @@ static int snd_pcm_oss_period_size(struc

    oss_buffer_size = snd_pcm_plug_client_size(substream,
    snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_BUFFER_SIZE, NULL)) * oss_frame_size;
    + if (!oss_buffer_size)
    + return -EINVAL;
    oss_buffer_size = rounddown_pow_of_two(oss_buffer_size);
    if (atomic_read(&substream->mmap_count)) {
    if (oss_buffer_size > runtime->oss.mmap_bytes)
    @@ -743,17 +745,21 @@ static int snd_pcm_oss_period_size(struc

    min_period_size = snd_pcm_plug_client_size(substream,
    snd_pcm_hw_param_value_min(slave_params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, NULL));
    - min_period_size *= oss_frame_size;
    - min_period_size = roundup_pow_of_two(min_period_size);
    - if (oss_period_size < min_period_size)
    - oss_period_size = min_period_size;
    + if (min_period_size) {
    + min_period_size *= oss_frame_size;
    + min_period_size = roundup_pow_of_two(min_period_size);
    + if (oss_period_size < min_period_size)
    + oss_period_size = min_period_size;
    + }

    max_period_size = snd_pcm_plug_client_size(substream,
    snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, NULL));
    - max_period_size *= oss_frame_size;
    - max_period_size = rounddown_pow_of_two(max_period_size);
    - if (oss_period_size > max_period_size)
    - oss_period_size = max_period_size;
    + if (max_period_size) {
    + max_period_size *= oss_frame_size;
    + max_period_size = rounddown_pow_of_two(max_period_size);
    + if (oss_period_size > max_period_size)
    + oss_period_size = max_period_size;
    + }

    oss_periods = oss_buffer_size / oss_period_size;


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