From 37b12c16beb6f6c1c3c678c1aacbc46525c250f7 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Fri, 6 May 2022 12:10:12 +0300 Subject: ALSA: pcm: Fix races among concurrent prealloc proc writes commit 69534c48ba8ce552ce383b3dfdb271ffe51820c3 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: Reviewed-by: Jaroslav Kysela Link: https://lore.kernel.org/r/20220322170720.3529-5-tiwai@suse.de Signed-off-by: Takashi Iwai [OP: backport to 5.4: adjusted context] Signed-off-by: Ovidiu Panait Signed-off-by: Greg Kroah-Hartman --- sound/core/pcm_memory.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c index 7600dcdf5fd4..9aea1d6fb054 100644 --- a/sound/core/pcm_memory.c +++ b/sound/core/pcm_memory.c @@ -133,19 +133,20 @@ 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) { @@ -153,7 +154,7 @@ 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 { @@ -165,6 +166,8 @@ 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) -- cgit v1.2.3