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ALSA: pcm: Fix races among concurrent prealloc proc writes

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We have no protection against concurrent PCM buffer preallocation
changes via proc files, and it may potentially lead to UAF or some
weird problem.  This patch applies the PCM open_mutex to the proc
write operation for avoiding the racy proc writes and the PCM stream
open (and further operations).

Cc: <stable@vger.kernel.org>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220322170720.3529-5-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2022-03-22 18:07:20 +01:00
parent 3c3201f8c7
commit 69534c48ba
1 changed files with 7 additions and 4 deletions
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11
sound/core/pcm_memory.c
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@ -163,19 +163,20 @@ static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
size_t size;
struct snd_dma_buffer new_dmab;
mutex_lock(&substream->pcm->open_mutex);
if (substream->runtime) {
buffer->error = -EBUSY;
return;
goto unlock;
}
if (!snd_info_get_line(buffer, line, sizeof(line))) {
snd_info_get_str(str, line, sizeof(str));
size = simple_strtoul(str, NULL, 10) * 1024;
if ((size != 0 && size < 8192) || size > substream->dma_max) {
buffer->error = -EINVAL;
return;
goto unlock;
}
if (substream->dma_buffer.bytes == size)
return;
goto unlock;
memset(&new_dmab, 0, sizeof(new_dmab));
new_dmab.dev = substream->dma_buffer.dev;
if (size > 0) {
@ -189,7 +190,7 @@ static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
substream->pcm->card->number, substream->pcm->device,
substream->stream ? 'c' : 'p', substream->number,
substream->pcm->name, size);
return;
goto unlock;
}
substream->buffer_bytes_max = size;
} else {
@ -201,6 +202,8 @@ static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
} else {
buffer->error = -EINVAL;
}
unlock:
mutex_unlock(&substream->pcm->open_mutex);
}
static inline void preallocate_info_init(struct snd_pcm_substream *substream)