• Takashi Iwai's avatar
    ALSA: pcm: Return -EBUSY for OSS ioctls changing busy streams · 40cab6e8
    Takashi Iwai authored
    OSS PCM stream management isn't modal but it allows ioctls issued at
    any time for changing the parameters.  In the previous hardening
    patch ("ALSA: pcm: Avoid potential races between OSS ioctls and
    read/write"), we covered these races and prevent the corruption by
    protecting the concurrent accesses via params_lock mutex.  However,
    this means that some ioctls that try to change the stream parameter
    (e.g. channels or format) would be blocked until the read/write
    finishes, and it may take really long.
    
    Basically changing the parameter while reading/writing is an invalid
    operation, hence it's even more user-friendly from the API POV if it
    returns -EBUSY in such a situation.
    
    This patch adds such checks in the relevant ioctls with the addition
    of read/write access refcount.
    
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
    40cab6e8
pcm_oss.h 2.69 KB