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authorTakashi Iwai <tiwai@suse.de>2022-03-22 18:07:20 +0100
committerTakashi Iwai <tiwai@suse.de>2022-03-22 20:56:58 +0100
commit69534c48ba8ce552ce383b3dfdb271ffe51820c3 (patch)
tree5dd87d340078126220bb58f2594d0550e9235155 /sound/core
parent3c3201f8c7bb77eb53b08a3ca8d9a4ddc500b4c0 (diff)
downloadlinux-69534c48ba8ce552ce383b3dfdb271ffe51820c3.tar.bz2
ALSA: pcm: Fix races among concurrent prealloc proc writes
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>
Diffstat (limited to 'sound/core')
-rw-r--r--sound/core/pcm_memory.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index b70ce3b69ab4..8848d2f3160d 100644
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -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)