From: Takashi Iwai <tiwai@xxxxxxx>
This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.
===============
[ 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@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
sound/core/timer.c | 34 +++++++++++++++-------------------
1 file changed, 15 insertions(+), 19 deletions(-)
diff --git a/sound/core/timer.c b/sound/core/timer.c
index 46ac1ae..4927a3c 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;
}
--
2.5.0
--
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