Commit 88a06d6f authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: rawmidi: Access runtime->avail always in spinlock 



The runtime->avail field may be accessed concurrently while some
places refer to it without taking the runtime->lock spinlock, as
detected by KCSAN.  Usually this isn't a big problem, but for
consistency and safety, we should take the spinlock at each place
referencing this field.

Reported-by: default avatar <syzbot+a23a6f1215c84756577c@syzkaller.appspotmail.com>
Reported-by: default avatar <syzbot+3d367d1df1d2b67f5c19@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/20201206083527.21163-1-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 4ebd4703

sound/core/rawmidi.c

+35 −14
Original line number Diff line number Diff line
@@ -95,11 +95,21 @@ static inline unsigned short snd_rawmidi_file_flags(struct file *file) 
	}

}



static inline int snd_rawmidi_ready(struct snd_rawmidi_substream *substream)

static inline bool __snd_rawmidi_ready(struct snd_rawmidi_runtime *runtime)

{

	return runtime->avail >= runtime->avail_min;

}



static bool snd_rawmidi_ready(struct snd_rawmidi_substream *substream)

{

	struct snd_rawmidi_runtime *runtime = substream->runtime;

	unsigned long flags;

	bool ready;



	return runtime->avail >= runtime->avail_min;

	spin_lock_irqsave(&runtime->lock, flags);

	ready = __snd_rawmidi_ready(runtime);

	spin_unlock_irqrestore(&runtime->lock, flags);

	return ready;

}



static inline int snd_rawmidi_ready_append(struct snd_rawmidi_substream *substream,
@@ -1019,7 +1029,7 @@ int snd_rawmidi_receive(struct snd_rawmidi_substream *substream, 
	if (result > 0) {

		if (runtime->event)

			schedule_work(&runtime->event_work);

		else if (snd_rawmidi_ready(substream))

		else if (__snd_rawmidi_ready(runtime))

			wake_up(&runtime->sleep);

	}

	spin_unlock_irqrestore(&runtime->lock, flags);
@@ -1098,7 +1108,7 @@ static ssize_t snd_rawmidi_read(struct file *file, char __user *buf, size_t coun 
	result = 0;

	while (count > 0) {

		spin_lock_irq(&runtime->lock);

		while (!snd_rawmidi_ready(substream)) {

		while (!__snd_rawmidi_ready(runtime)) {

			wait_queue_entry_t wait;



			if ((file->f_flags & O_NONBLOCK) != 0 || result > 0) {
@@ -1115,9 +1125,11 @@ static ssize_t snd_rawmidi_read(struct file *file, char __user *buf, size_t coun 
				return -ENODEV;

			if (signal_pending(current))

				return result > 0 ? result : -ERESTARTSYS;

			if (!runtime->avail)

				return result > 0 ? result : -EIO;

			spin_lock_irq(&runtime->lock);

			if (!runtime->avail) {

				spin_unlock_irq(&runtime->lock);

				return result > 0 ? result : -EIO;

			}

		}

		spin_unlock_irq(&runtime->lock);

		count1 = snd_rawmidi_kernel_read1(substream,
@@ -1255,7 +1267,7 @@ int __snd_rawmidi_transmit_ack(struct snd_rawmidi_substream *substream, int coun 
	runtime->avail += count;

	substream->bytes += count;

	if (count > 0) {

		if (runtime->drain || snd_rawmidi_ready(substream))

		if (runtime->drain || __snd_rawmidi_ready(runtime))

			wake_up(&runtime->sleep);

	}

	return count;
@@ -1444,9 +1456,11 @@ static ssize_t snd_rawmidi_write(struct file *file, const char __user *buf, 
				return -ENODEV;

			if (signal_pending(current))

				return result > 0 ? result : -ERESTARTSYS;

			if (!runtime->avail && !timeout)

				return result > 0 ? result : -EIO;

			spin_lock_irq(&runtime->lock);

			if (!runtime->avail && !timeout) {

				spin_unlock_irq(&runtime->lock);

				return result > 0 ? result : -EIO;

			}

		}

		spin_unlock_irq(&runtime->lock);

		count1 = snd_rawmidi_kernel_write1(substream, buf, NULL, count);
@@ -1526,6 +1540,7 @@ static void snd_rawmidi_proc_info_read(struct snd_info_entry *entry, 
	struct snd_rawmidi *rmidi;

	struct snd_rawmidi_substream *substream;

	struct snd_rawmidi_runtime *runtime;

	unsigned long buffer_size, avail, xruns;



	rmidi = entry->private_data;

	snd_iprintf(buffer, "%s\n\n", rmidi->name);
@@ -1544,13 +1559,16 @@ static void snd_rawmidi_proc_info_read(struct snd_info_entry *entry, 
				    "  Owner PID    : %d\n",

				    pid_vnr(substream->pid));

				runtime = substream->runtime;

				spin_lock_irq(&runtime->lock);

				buffer_size = runtime->buffer_size;

				avail = runtime->avail;

				spin_unlock_irq(&runtime->lock);

				snd_iprintf(buffer,

				    "  Mode         : %s\n"

				    "  Buffer size  : %lu\n"

				    "  Avail        : %lu\n",

				    runtime->oss ? "OSS compatible" : "native",

				    (unsigned long) runtime->buffer_size,

				    (unsigned long) runtime->avail);

				    buffer_size, avail);

			}

		}

	}
@@ -1568,13 +1586,16 @@ static void snd_rawmidi_proc_info_read(struct snd_info_entry *entry, 
					    "  Owner PID    : %d\n",

					    pid_vnr(substream->pid));

				runtime = substream->runtime;

				spin_lock_irq(&runtime->lock);

				buffer_size = runtime->buffer_size;

				avail = runtime->avail;

				xruns = runtime->xruns;

				spin_unlock_irq(&runtime->lock);

				snd_iprintf(buffer,

					    "  Buffer size  : %lu\n"

					    "  Avail        : %lu\n"

					    "  Overruns     : %lu\n",

					    (unsigned long) runtime->buffer_size,

					    (unsigned long) runtime->avail,

					    (unsigned long) runtime->xruns);

					    buffer_size, avail, xruns);

			}

		}

	}

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