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>

diff --git a/drivers/ieee1394/raw1394.c b/drivers/ieee1394/raw1394.c
index d159442..2cf4ae7 100644 (file)
--- 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 {