ALSA: pcm: Improve the fix for race of buffer access at PCM OSS layer

Handle the error code from snd_pcm_buffer_access_lock() in
snd_pcm_runtime_buffer_set_silence() function.

Found by Alexandros Panagiotou <apanagio@redhat.com>

Fixes: 93a81ca ("ALSA: pcm: Fix race of buffer access at PCM OSS layer")
Cc: stable@vger.kernel.org # 6.15
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Link: https://patch.msgid.link/20260107213642.332954-1-perex@perex.cz
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: perexg

include/sound/pcm.h

@@ -1402,7 +1402,7 @@ int snd_pcm_lib_mmap_iomem(struct snd_pcm_substream *substream, struct vm_area_s
 #define snd_pcm_lib_mmap_iomem	NULL
 #endif
 
-void snd_pcm_runtime_buffer_set_silence(struct snd_pcm_runtime *runtime);
+int snd_pcm_runtime_buffer_set_silence(struct snd_pcm_runtime *runtime);
 
 /**
  * snd_pcm_limit_isa_dma_size - Get the max size fitting with ISA DMA transfer

sound/core/oss/pcm_oss.c

@@ -1074,7 +1074,9 @@ static int snd_pcm_oss_change_params_locked(struct snd_pcm_substream *substream)
 	runtime->oss.params = 0;
 	runtime->oss.prepare = 1;
 	runtime->oss.buffer_used = 0;
-	snd_pcm_runtime_buffer_set_silence(runtime);
+	err = snd_pcm_runtime_buffer_set_silence(runtime);
+	if (err < 0)
+		goto failure;
 
 	runtime->oss.period_frames = snd_pcm_alsa_frames(substream, oss_period_size);
 

sound/core/pcm_native.c

@@ -730,13 +730,18 @@ static void snd_pcm_buffer_access_unlock(struct snd_pcm_runtime *runtime)
 }
 
 /* fill the PCM buffer with the current silence format; called from pcm_oss.c */
-void snd_pcm_runtime_buffer_set_silence(struct snd_pcm_runtime *runtime)
+int snd_pcm_runtime_buffer_set_silence(struct snd_pcm_runtime *runtime)
 {
-	snd_pcm_buffer_access_lock(runtime);
+	int err;
+
+	err = snd_pcm_buffer_access_lock(runtime);
+	if (err < 0)
+		return err;
 	if (runtime->dma_area)
 		snd_pcm_format_set_silence(runtime->format, runtime->dma_area,
 					   bytes_to_samples(runtime, runtime->dma_bytes));
 	snd_pcm_buffer_access_unlock(runtime);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(snd_pcm_runtime_buffer_set_silence);