diff options
| author | Takashi Iwai <tiwai@suse.de> | 2016-02-08 17:26:58 +0100 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2016-03-04 10:18:39 -0500 |
| commit | 0f97e402030cb82e5a5ab9ca9babf323d1bc5b74 (patch) | |
| tree | 05d5360fb5cdff903f5e2529f23c0be1d3645b46 | |
| parent | 8d155bee64261fb1c65ee5526af85f74290f574f (diff) | |
| download | lwn-0f97e402030cb82e5a5ab9ca9babf323d1bc5b74.tar.gz lwn-0f97e402030cb82e5a5ab9ca9babf323d1bc5b74.zip | |
ALSA: timer: Fix race at concurrent reads
[ Upstream commit 4dff5c7b7093b19c19d3a100f8a3ad87cb7cd9e7 ]
snd_timer_user_read() has a potential race among parallel reads, as
qhead and qused are updated outside the critical section due to
copy_to_user() calls. Move them into the critical section, and also
sanitize the relevant code a bit.
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
| -rw-r--r-- | sound/core/timer.c | 34 |
1 files changed, 15 insertions, 19 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c index 46ac1ae790fc..4927a3c88340 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1922,6 +1922,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, { struct snd_timer_user *tu; long result = 0, unit; + int qhead; int err = 0; tu = file->private_data; @@ -1933,7 +1934,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, if ((file->f_flags & O_NONBLOCK) != 0 || result > 0) { err = -EAGAIN; - break; + goto _error; } set_current_state(TASK_INTERRUPTIBLE); @@ -1948,42 +1949,37 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, if (tu->disconnected) { err = -ENODEV; - break; + goto _error; } if (signal_pending(current)) { err = -ERESTARTSYS; - break; + goto _error; } } + qhead = tu->qhead++; + tu->qhead %= tu->queue_size; spin_unlock_irq(&tu->qlock); - if (err < 0) - goto _error; if (tu->tread) { - if (copy_to_user(buffer, &tu->tqueue[tu->qhead++], - sizeof(struct snd_timer_tread))) { + if (copy_to_user(buffer, &tu->tqueue[qhead], + sizeof(struct snd_timer_tread))) err = -EFAULT; - goto _error; - } } else { - if (copy_to_user(buffer, &tu->queue[tu->qhead++], - sizeof(struct snd_timer_read))) { + if (copy_to_user(buffer, &tu->queue[qhead], + sizeof(struct snd_timer_read))) err = -EFAULT; - goto _error; - } } - tu->qhead %= tu->queue_size; - - result += unit; - buffer += unit; - spin_lock_irq(&tu->qlock); tu->qused--; + if (err < 0) + goto _error; + result += unit; + buffer += unit; } - spin_unlock_irq(&tu->qlock); _error: + spin_unlock_irq(&tu->qlock); return result > 0 ? result : err; } |