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Subject[RFC patch 3/3] 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>
---
drivers/ieee1394/raw1394.c | 4 ++++
1 file changed, 4 insertions(+)
Index: linux/drivers/ieee1394/raw1394.c
===================================================================
--- linux.orig/drivers/ieee1394/raw1394.c
+++ linux/drivers/ieee1394/raw1394.c
@@ -2268,6 +2268,8 @@ static ssize_t raw1394_write(struct file
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
break;
}

+ mutex_unlock(&fi->state_mutex);
+
if (retval < 0) {
free_pending_request(req);
} else {
--
Stefan Richter
-=====-==--- =--- =----
http://arcgraph.de/sr/


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