On Thu, 01 Aug 2013 11:14:39 +0800 <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> The patch below does not apply to the 3.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
As requested. Thanks.
From: NeilBrown <neilb@xxxxxxx>
Date: Wed, 24 Jul 2013 15:37:42 +1000
Subject: [PATCH] md/raid10: remove use-after-free bug.
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.
Cc: stable@xxxxxxxxxxxxxxx (3.3+)
Signed-off-by: NeilBrown <neilb@xxxxxxx>
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 0cc7985..54ba531 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2029,12 +2029,18 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
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, wbio->bi_size >> 9);
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,
wbio2->bi_size >> 9);
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