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authorTakashi Iwai <tiwai@suse.de>2018-03-23 10:03:26 +0300
committerTakashi Iwai <tiwai@suse.de>2018-03-24 00:18:05 +0300
commit40cab6e88cb0b6c56d3f30b7491a20e803f948f6 (patch)
tree229da33d93b78fe63bab43877449301d32855af2 /include/sound/pcm_oss.h
parent02a5d6925cd34c3b774bdb8eefb057c40a30e870 (diff)
downloadlinux-40cab6e88cb0b6c56d3f30b7491a20e803f948f6.tar.xz
ALSA: pcm: Return -EBUSY for OSS ioctls changing busy streams
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: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'include/sound/pcm_oss.h')
-rw-r--r--include/sound/pcm_oss.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/sound/pcm_oss.h b/include/sound/pcm_oss.h
index 760c969d885d..12bbf8c81112 100644
--- a/include/sound/pcm_oss.h
+++ b/include/sound/pcm_oss.h
@@ -57,6 +57,7 @@ struct snd_pcm_oss_runtime {
char *buffer; /* vmallocated period */
size_t buffer_used; /* used length from period buffer */
struct mutex params_lock;
+ atomic_t rw_ref; /* concurrent read/write accesses */
#ifdef CONFIG_SND_PCM_OSS_PLUGINS
struct snd_pcm_plugin *plugin_first;
struct snd_pcm_plugin *plugin_last;