Revert "ALSA: rawmidi: Fix racy buffer resize under concurrent accesses"

This reverts commit 718eede1eeb602531e09191d3107eb849bbe64eb.
Remove the remaining parts of that commit as we use `realloc_mutex`
instead to protect the buffer and `buffer_ref` is effectively unused.

Change-Id: If0cf319ca5ab097751bc5e6753f61bd626d9e601

2 files changed, 6 insertions, 23 deletions

diff --git a/include/sound/rawmidi.h b/include/sound/rawmidi.h
index afffa756357a..3e0171ea47f3 100644
--- a/include/sound/rawmidi.h
+++ b/include/sound/rawmidi.h
@@ -76,7 +76,6 @@ struct snd_rawmidi_runtime {
 	size_t avail_min;	/* min avail for wakeup */
 	size_t avail;		/* max used buffer for wakeup */
 	size_t xruns;		/* over/underruns counter */
-	int buffer_ref;		/* buffer reference count */
 	/* misc */
 	spinlock_t lock;
 	struct mutex realloc_mutex;
diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index 108c75e35b39..a7a1b1c4cad9 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -108,17 +108,6 @@ static void snd_rawmidi_input_event_work(struct work_struct *work)
 		runtime->event(runtime->substream);
 }
 
-/* buffer refcount management: call with runtime->lock held */
-static inline void snd_rawmidi_buffer_ref(struct snd_rawmidi_runtime *runtime)
-{
-	runtime->buffer_ref++;
-}
-
-static inline void snd_rawmidi_buffer_unref(struct snd_rawmidi_runtime *runtime)
-{
-	runtime->buffer_ref--;
-}
-
 static int snd_rawmidi_runtime_create(struct snd_rawmidi_substream *substream)
 {
 	struct snd_rawmidi_runtime *runtime;
@@ -990,12 +979,10 @@ static long snd_rawmidi_kernel_read1(struct snd_rawmidi_substream *substream,
 	long result = 0, count1;
 	struct snd_rawmidi_runtime *runtime = substream->runtime;
 	unsigned long appl_ptr;
-	int err = 0;
 
 	if (userbuf)
 		mutex_lock(&runtime->realloc_mutex);
 	spin_lock_irqsave(&runtime->lock, flags);
-	snd_rawmidi_buffer_ref(runtime);
 	while (count > 0 && runtime->avail) {
 		count1 = runtime->buffer_size - runtime->appl_ptr;
 		if (count1 > count)
@@ -1014,21 +1001,20 @@ static long snd_rawmidi_kernel_read1(struct snd_rawmidi_substream *substream,
 		if (userbuf) {
 			spin_unlock_irqrestore(&runtime->lock, flags);
 			if (copy_to_user(userbuf + result,
-					 runtime->buffer + appl_ptr, count1))
-				err = -EFAULT;
+					 runtime->buffer + appl_ptr, count1)) {
+					mutex_unlock(&runtime->realloc_mutex);
+					return result > 0 ? result : -EFAULT;
+			}
+
 			spin_lock_irqsave(&runtime->lock, flags);
-			if (err)
-				goto out;
 		}
 		result += count1;
 		count -= count1;
 	}
- out:
-	snd_rawmidi_buffer_unref(runtime);
 	spin_unlock_irqrestore(&runtime->lock, flags);
 	if (userbuf)
 		mutex_unlock(&runtime->realloc_mutex);
-	return result > 0 ? result : err;
+	return result;
 }
 
 long snd_rawmidi_kernel_read(struct snd_rawmidi_substream *substream,
@@ -1303,7 +1289,6 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream,
 			return -EAGAIN;
 		}
 	}
-	snd_rawmidi_buffer_ref(runtime);
 	while (count > 0 && runtime->avail > 0) {
 		count1 = runtime->buffer_size - runtime->appl_ptr;
 		if (count1 > count)
@@ -1335,7 +1320,6 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream,
 	}
       __end:
 	count1 = runtime->avail < runtime->buffer_size;
-	snd_rawmidi_buffer_unref(runtime);
 	spin_unlock_irqrestore(&runtime->lock, flags);
 	if (userbuf)
 		mutex_unlock(&runtime->realloc_mutex);