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Subject[ 48/99] md/raid10: remove use-after-free bug.
Date
3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@suse.de>

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
using.

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@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2268,12 +2268,18 @@ 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) {
atomic_inc(&conf->mirrors[d].rdev->nr_pending);
md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));
generic_make_request(wbio);
}
- if (wbio2 && wbio2->bi_end_io) {
+ if (wbio2) {
atomic_inc(&conf->mirrors[d].replacement->nr_pending);
md_sync_acct(conf->mirrors[d].replacement->bdev,
bio_sectors(wbio2));



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