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authorJeff Dike <jdike@addtoit.com>2007-07-15 23:38:47 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:38 -0700
commit0a6d3a2a3813e7b25267366cfbf9a4a4698dd1c2 (patch)
tree98b0c20ad616258dae150a04307ce3a2ad90adf1 /arch/um
parent7ff9057db7edeb210fd5c00314c52154922d8868 (diff)
downloadlinux-2.6.34-ux500-0a6d3a2a3813e7b25267366cfbf9a4a4698dd1c2.tar.gz
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>
Diffstat (limited to 'arch/um')
-rw-r--r--arch/um/drivers/ubd_kern.c6
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;