This is a note to let you know that I've just added the patch titled md/raid5: limit request size according to implementation limits to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: md-raid5-limit-request-size-according-to-implementation-limits.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From e8d7c33232e5fdfa761c3416539bc5b4acd12db5 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Date: Sun, 27 Nov 2016 19:32:32 +0300 Subject: md/raid5: limit request size according to implementation limits From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> commit e8d7c33232e5fdfa761c3416539bc5b4acd12db5 upstream. Current implementation employ 16bit counter of active stripes in lower bits of bio->bi_phys_segments. If request is big enough to overflow this counter bio will be completed and freed too early. Fortunately this not happens in default configuration because several other limits prevent that: stripe_cache_size * nr_disks effectively limits count of active stripes. And small max_sectors_kb at lower disks prevent that during normal read/write operations. Overflow easily happens in discard if it's enabled by module parameter "devices_handle_discard_safely" and stripe_cache_size is set big enough. This patch limits requests size with 256Mb - 8Kb to prevent overflows. Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Cc: Shaohua Li <shli@xxxxxxxxxx> Cc: Neil Brown <neilb@xxxxxxxx> Signed-off-by: Shaohua Li <shli@xxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/raid5.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -6984,6 +6984,15 @@ static int raid5_run(struct mddev *mddev stripe = (stripe | (stripe-1)) + 1; mddev->queue->limits.discard_alignment = stripe; mddev->queue->limits.discard_granularity = stripe; + + /* + * We use 16-bit counter of active stripes in bi_phys_segments + * (minus one for over-loaded initialization) + */ + blk_queue_max_hw_sectors(mddev->queue, 0xfffe * STRIPE_SECTORS); + blk_queue_max_discard_sectors(mddev->queue, + 0xfffe * STRIPE_SECTORS); + /* * unaligned part of discard request will be ignored, so can't * guarantee discard_zeroes_data Patches currently in stable-queue which might be from khlebnikov@xxxxxxxxxxxxxx are queue-4.9/md-raid5-limit-request-size-according-to-implementation-limits.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html