From bbfa49a9523a1f17687bf199689a0b369624259d Mon Sep 17 00:00:00 2001 From: Daniel Rosenberg Date: Tue, 31 Oct 2017 16:55:26 -0700 Subject: [PATCH] ANDROID: sound: rawmidi: Hold lock around realloc The SNDRV_RAWMIDI_STREAM_{OUTPUT,INPUT} ioctls may reallocate runtime->buffer while other kernel threads are accessing it. If the underlying krealloc() call frees the original buffer, then this can turn into a use-after-free. Most of these accesses happen while the thread is holding runtime->lock, and can be fixed by just holding the same lock while replacing runtime->buffer, however we can't hold this spinlock while snd_rawmidi_kernel_{read1,write1} are copying to/from userspace. We need to add and acquire a new mutex to prevent this from happening concurrently with reallocation. We hold this mutex during the entire reallocation process, to also prevent multiple concurrent reallocations leading to a double-free. Signed-off-by: Daniel Rosenberg bug: 64315347 Change-Id: I05764d4f1a38f373eb7c0ac1c98607ee5ff0eded [dcagle@codeaurora.org: Resolve trivial merge conflict] Git-repo: https://android.googlesource.com/kernel/msm Git-commit: d7193540482d11ff0ad3a07fc18717811641c6eb Signed-off-by: Dennis Cagle Signed-off-by: Aaditya Vohra --- include/sound/rawmidi.h | 1 + sound/core/rawmidi.c | 44 ++++++++++++++++++++++++++++++++++++----- 2 files changed, 40 insertions(+), 5 deletions(-) diff --git a/include/sound/rawmidi.h b/include/sound/rawmidi.h index 6665cb29e1a2..9955e0b85de5 100644 --- a/include/sound/rawmidi.h +++ b/include/sound/rawmidi.h @@ -78,6 +78,7 @@ struct snd_rawmidi_runtime { size_t xruns; /* over/underruns counter */ /* misc */ spinlock_t lock; + struct mutex realloc_mutex; wait_queue_head_t sleep; /* event handler (new bytes, input only) */ void (*event)(struct snd_rawmidi_substream *substream); diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c index f055ca10bbc1..4b44386d5d22 100644 --- a/sound/core/rawmidi.c +++ b/sound/core/rawmidi.c @@ -115,6 +115,7 @@ static int snd_rawmidi_runtime_create(struct snd_rawmidi_substream *substream) return -ENOMEM; runtime->substream = substream; spin_lock_init(&runtime->lock); + mutex_init(&runtime->realloc_mutex); init_waitqueue_head(&runtime->sleep); INIT_WORK(&runtime->event_work, snd_rawmidi_input_event_work); runtime->event = NULL; @@ -636,8 +637,10 @@ int snd_rawmidi_output_params(struct snd_rawmidi_substream *substream, struct snd_rawmidi_params * params) { char *newbuf; + char *oldbuf; struct snd_rawmidi_runtime *runtime = substream->runtime; - + unsigned long flags; + if (substream->append && substream->use_count > 1) return -EBUSY; snd_rawmidi_drain_output(substream); @@ -648,13 +651,22 @@ int snd_rawmidi_output_params(struct snd_rawmidi_substream *substream, return -EINVAL; } if (params->buffer_size != runtime->buffer_size) { - newbuf = krealloc(runtime->buffer, params->buffer_size, + mutex_lock(&runtime->realloc_mutex); + newbuf = __krealloc(runtime->buffer, params->buffer_size, GFP_KERNEL); - if (!newbuf) + if (!newbuf) { + mutex_unlock(&runtime->realloc_mutex); return -ENOMEM; + } + spin_lock_irqsave(&runtime->lock, flags); + oldbuf = runtime->buffer; runtime->buffer = newbuf; runtime->buffer_size = params->buffer_size; runtime->avail = runtime->buffer_size; + spin_unlock_irqrestore(&runtime->lock, flags); + if (oldbuf != newbuf) + kfree(oldbuf); + mutex_unlock(&runtime->realloc_mutex); } runtime->avail_min = params->avail_min; substream->active_sensing = !params->no_active_sensing; @@ -666,7 +678,9 @@ int snd_rawmidi_input_params(struct snd_rawmidi_substream *substream, struct snd_rawmidi_params * params) { char *newbuf; + char *oldbuf; struct snd_rawmidi_runtime *runtime = substream->runtime; + unsigned long flags; snd_rawmidi_drain_input(substream); if (params->buffer_size < 32 || params->buffer_size > 1024L * 1024L) { @@ -676,12 +690,21 @@ int snd_rawmidi_input_params(struct snd_rawmidi_substream *substream, return -EINVAL; } if (params->buffer_size != runtime->buffer_size) { - newbuf = krealloc(runtime->buffer, params->buffer_size, + mutex_lock(&runtime->realloc_mutex); + newbuf = __krealloc(runtime->buffer, params->buffer_size, GFP_KERNEL); - if (!newbuf) + if (!newbuf) { + mutex_unlock(&runtime->realloc_mutex); return -ENOMEM; + } + spin_lock_irqsave(&runtime->lock, flags); + oldbuf = runtime->buffer; runtime->buffer = newbuf; runtime->buffer_size = params->buffer_size; + spin_unlock_irqrestore(&runtime->lock, flags); + if (oldbuf != newbuf) + kfree(oldbuf); + mutex_unlock(&runtime->realloc_mutex); } runtime->avail_min = params->avail_min; return 0; @@ -954,6 +977,8 @@ static long snd_rawmidi_kernel_read1(struct snd_rawmidi_substream *substream, unsigned long appl_ptr; spin_lock_irqsave(&runtime->lock, flags); + if (userbuf) + mutex_lock(&runtime->realloc_mutex); while (count > 0 && runtime->avail) { count1 = runtime->buffer_size - runtime->appl_ptr; if (count1 > count) @@ -973,6 +998,7 @@ static long snd_rawmidi_kernel_read1(struct snd_rawmidi_substream *substream, spin_unlock_irqrestore(&runtime->lock, flags); if (copy_to_user(userbuf + result, runtime->buffer + appl_ptr, count1)) { + mutex_unlock(&runtime->realloc_mutex); return result > 0 ? result : -EFAULT; } spin_lock_irqsave(&runtime->lock, flags); @@ -981,6 +1007,8 @@ static long snd_rawmidi_kernel_read1(struct snd_rawmidi_substream *substream, count -= count1; } spin_unlock_irqrestore(&runtime->lock, flags); + if (userbuf) + mutex_unlock(&runtime->realloc_mutex); return result; } @@ -1245,10 +1273,14 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream, return -EINVAL; result = 0; + if (userbuf) + mutex_lock(&runtime->realloc_mutex); spin_lock_irqsave(&runtime->lock, flags); if (substream->append) { if ((long)runtime->avail < count) { spin_unlock_irqrestore(&runtime->lock, flags); + if (userbuf) + mutex_unlock(&runtime->realloc_mutex); return -EAGAIN; } } @@ -1284,6 +1316,8 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream, __end: count1 = runtime->avail < runtime->buffer_size; spin_unlock_irqrestore(&runtime->lock, flags); + if (userbuf) + mutex_unlock(&runtime->realloc_mutex); if (count1) snd_rawmidi_output_trigger(substream, 1); return result;