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ALSA: pcm: Fix races among concurrent prealloc proc writes

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commit 69534c48ba upstream.

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>
[OP: backport to 4.19: adjusted context]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Takashi Iwai 2022-05-13 11:00:17 +03:00 committed by Greg Kroah-Hartman
parent 47cef5937a
commit e14dca613e
1 changed files with 7 additions and 4 deletions
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11
sound/core/pcm_memory.c
View file

@ -160,19 +160,20 @@ 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) {
@ -180,7 +181,7 @@ static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
substream->dma_buffer.dev.dev,
size, &new_dmab) < 0) {
buffer->error = -ENOMEM;
return;
goto unlock;
}
substream->buffer_bytes_max = size;
} else {
@ -192,6 +193,8 @@ 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)