diff options
| author | Jeff Dike <jdike@addtoit.com> | 2007-07-15 23:38:47 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-16 09:05:38 -0700 |
| commit | 0a6d3a2a3813e7b25267366cfbf9a4a4698dd1c2 (patch) | |
| tree | 98b0c20ad616258dae150a04307ce3a2ad90adf1 | |
| parent | 7ff9057db7edeb210fd5c00314c52154922d8868 (diff) | |
uml: fix request->sector update
It is theoretically possible for a request to finish and be freed between
writing it to the I/O thread and updating the sector count. In this case, the
update will dereference a freed pointer.
To avoid this, I delay the update until processing the next sg segment, when
the request pointer is known to be good.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/um/drivers/ubd_kern.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c index 2e09f162c42..0947f2e2004 100644 --- a/arch/um/drivers/ubd_kern.c +++ b/arch/um/drivers/ubd_kern.c @@ -1083,7 +1083,7 @@ static void do_ubd_request(request_queue_t *q) { struct io_thread_req *io_req; struct request *req; - int n; + int n, last_sectors; while(1){ struct ubd *dev = q->queuedata; @@ -1099,9 +1099,11 @@ static void do_ubd_request(request_queue_t *q) } req = dev->request; + last_sectors = 0; while(dev->start_sg < dev->end_sg){ struct scatterlist *sg = &dev->sg[dev->start_sg]; + req->sector += last_sectors; io_req = kmalloc(sizeof(struct io_thread_req), GFP_ATOMIC); if(io_req == NULL){ @@ -1113,6 +1115,7 @@ static void do_ubd_request(request_queue_t *q) (unsigned long long) req->sector << 9, sg->offset, sg->length, sg->page); + last_sectors = sg->length >> 9; n = os_write_file(thread_fd, &io_req, sizeof(struct io_thread_req *)); if(n != sizeof(struct io_thread_req *)){ @@ -1124,7 +1127,6 @@ static void do_ubd_request(request_queue_t *q) return; } - req->sector += sg->length >> 9; dev->start_sg++; } dev->end_sg = 0; |