From: Kevin Vigor kvigor@gmail.com

In __make_request() a new r10bio is allocated and passed to raid10_read_request(). The read_slot member of the bio is not initialized, and the raid10_read_request() uses it to index an array. This leads to occasional panics.

Fix by initializing the field to invalid value and checking for valid value in raid10_read_request().

Cc: stable@vger.kernel.org # v4.14+ Signed-off-by: Kevin Vigor kvigor@gmail.com Signed-off-by: Song Liu songliubraving@fb.com (cherry picked from commit 93decc563637c4288380912eac0eb42fb246cc04) --- drivers/md/raid10.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index d08d77b9674ff..419ecdd914f4c 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -1120,7 +1120,7 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio, struct md_rdev *err_rdev = NULL; gfp_t gfp = GFP_NOIO;

- if (r10_bio->devs[slot].rdev) { + if (slot >= 0 && r10_bio->devs[slot].rdev) { /* * This is an error retry, but we cannot * safely dereference the rdev in the r10_bio, @@ -1513,6 +1513,7 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors) r10_bio->mddev = mddev; r10_bio->sector = bio->bi_iter.bi_sector; r10_bio->state = 0; + r10_bio->read_slot = -1; memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) * conf->copies);

if (bio_data_dir(bio) == READ)