V4L/DVB (8108): Fix open/close race in saa7134

The saa7134 driver uses a (non-atomic) variable in an attempt to
only allow one opener of the device (how it deals with sending
the fd over unix sockets I don't know).

Unfortunately, the release function first decrements this variable,
and THEN goes on to disable more of the device. This allows for
a race where another opener of the device comes in after the decrement of
the variable, configures the hardware just to then see the hardware
be disabled by the rest of the release function.

This patch makes the release function use the same lock as the open
function to protect the hardware as well as the variable (which now
at least has some locking to protect it).

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

diff --git a/drivers/media/video/saa7134/saa7134-empress.c b/drivers/media/video/saa7134/saa7134-empress.c
index 1c8cd0ef4a6502718e21906d618f4b6ab7cf5dac..3ae71a3408223800ce442efc413c8589bb18ae4a 100644 (file)
--- a/drivers/media/video/saa7134/saa7134-empress.c
+++ b/drivers/media/video/saa7134/saa7134-empress.c
@@ -110,6 +110,8 @@ static int ts_release(struct inode *inode, struct file *file)
 {
        struct saa7134_dev *dev = file->private_data;
 
+       mutex_lock(&dev->empress_tsq.vb_lock);
+
        videobuf_stop(&dev->empress_tsq);
        videobuf_mmap_free(&dev->empress_tsq);
 
@@ -122,6 +124,8 @@ static int ts_release(struct inode *inode, struct file *file)
 
        dev->empress_users--;
 
+       mutex_unlock(&dev->empress_tsq.vb_lock);
+
        return 0;
 }