From e91fee6f7f2a7f61aa89539e955c99c12a9ba4e4 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Mon, 13 Jun 2022 08:27:20 +0000 Subject: [PATCH] ALSA: pcm: Fix races among concurrent prealloc proc writes stable inclusion from linux-4.19.243 commit e14dca613e0a6ddc2bf6e360f16936a9f865205b category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I50WAS CVE: CVE-2022-1048 -------------------------------- 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 4.19: adjusted context] Signed-off-by: Ovidiu Panait Signed-off-by: Greg Kroah-Hartman Signed-off-by: Rui Xiang Reviewed-by: zhangxiaoxu Reviewed-by: Xiu Jianfeng Signed-off-by: Yongqiang Liu --- 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 4b5356a10315..48e5f0091ce4 100644 --- a/sound/core/pcm_memory.c +++ b/sound/core/pcm_memory.c @@ -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) -- GitLab