[ 32/39] md/raid10: remove use-after-free bug.

From: Greg Kroah-Hartman
Date: Fri Aug 02 2013 - 06:21:47 EST

3.4-stable review patch. If anyone has any objections, please let me know.


From: NeilBrown <neilb@xxxxxxx>

commit 0eb25bb027a100f5a9df8991f2f628e7d851bc1e upstream.

We always need to be careful when calling generic_make_request, as it
can start a chain of events which might free something that we are

Here is one place I wasn't careful enough. If the wbio2 is not in
use, then it might get freed at the first generic_make_request call.
So perform all necessary tests first.

This bug was introduced in 3.3-rc3 (24afd80d99) and can cause an
oops, so fix is suitable for any -stable since then.

Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/md/raid10.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2029,12 +2029,18 @@ static void recovery_request_write(struc
d = r10_bio->devs[1].devnum;
wbio = r10_bio->devs[1].bio;
wbio2 = r10_bio->devs[1].repl_bio;
+ /* Need to test wbio2->bi_end_io before we call
+ * generic_make_request as if the former is NULL,
+ * the latter is free to free wbio2.
+ */
+ if (wbio2 && !wbio2->bi_end_io)
+ wbio2 = NULL;
if (wbio->bi_end_io) {
md_sync_acct(conf->mirrors[d].rdev->bdev, wbio->bi_size >> 9);
- if (wbio2 && wbio2->bi_end_io) {
+ if (wbio2) {
wbio2->bi_size >> 9);

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