[PATCH 4.19 20/29] ALSA: rawmidi: Access runtime->avail always in spinlock

Greg Kroah-Hartman
2021-01-05T09:29:50Z

From: Takashi Iwai <tiwai@suse.de>

commit 88a06d6fd6b369d88cec46c62db3e2604a2f50d5 upstream.

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: syzbot+a23a6f1215c84756577c@syzkaller.appspotmail.com
Reported-by: syzbot+3d367d1df1d2b67f5c19@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20201206083527.21163-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
sound/core/rawmidi.c | 49 +++++++++++++++++++++++++++++++++++--------------
1 file changed, 35 insertions(+), 14 deletions(-)

--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -87,11 +87,21 @@ static inline unsigned short snd_rawmidi
}
}

-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,
@@ -960,7 +970,7 @@ int snd_rawmidi_receive(struct snd_rawmi
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);
@@ -1039,7 +1049,7 @@ static ssize_t snd_rawmidi_read(struct f
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) {
@@ -1056,9 +1066,11 @@ static ssize_t snd_rawmidi_read(struct f
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,
@@ -1196,7 +1208,7 @@ int __snd_rawmidi_transmit_ack(struct sn
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;
@@ -1363,9 +1375,11 @@ static ssize_t snd_rawmidi_write(struct
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);
@@ -1445,6 +1459,7 @@ static void snd_rawmidi_proc_info_read(s
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);
@@ -1463,13 +1478,16 @@ static void snd_rawmidi_proc_info_read(s
" 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);
}
}
}
@@ -1487,13 +1505,16 @@ static void snd_rawmidi_proc_info_read(s
" 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);
}
}
}