ieee1394: raw1394: make write() thread-safe

Application programs should use a libraw1394 handle only in a single
thread.  The raw1394 driver was apparently relying on this, because it
did nothing to protect its fi->state variable from corruption due to
concurrent accesses.

We now serialize the fi->state accesses.  This affects the write() path.
We re-use the state_mutex which was introduced to protect fi->iso_state
accesses in the ioctl() path.  These paths and accesses are independent
of each other, hence separate mutexes could be used.  But I don't see
much benefit in that.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/ieee1394/raw1394.c b/drivers/ieee1394/raw1394.c
index d1594427601f..2cf4ae75beca 100644
--- a/drivers/ieee1394/raw1394.c
+++ b/drivers/ieee1394/raw1394.c
@@ -2268,6 +2268,8 @@ static ssize_t raw1394_write(struct file *file, const char __user * buffer,
                 return -EFAULT;
         }
 
+        mutex_lock(&fi->state_mutex);
+
         switch (fi->state) {
         case opened:
                 retval = state_opened(fi, req);
@@ -2282,6 +2284,8 @@ static ssize_t raw1394_write(struct file *file, const char __user * buffer,
                 break;
         }
 
+        mutex_unlock(&fi->state_mutex);
+
         if (retval < 0) {
                 free_pending_request(req);
         } else {