Messages in this thread | | | From | Jeff Moyer <> | Subject | Re: [PATCH] block: copy bi_vcnt in __bio_clone_fast | Date | Thu, 09 Oct 2014 09:53:58 -0400 |
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Jeff Mahoney <jeffm@suse.com> writes:
> Commit 05f1dd53152173 (block: add queue flag for disabling SG merging) uses > bi_vcnt to assign bio->bi_phys_segments if sg merging is disabled. When > using device mapper on top of a blk-mq device (virtio_blk in my test), > we'd end up overflowing the scatterlist in __blk_bios_map_sg. > > __bio_clone_fast copies bi_iter and bi_io_vec but not bi_vcnt, so > blk_recount_segments would report bi_phys_segments as 0. Since > rq->nr_phys_segments is 0 as well, the checks to ensure that we don't > exceed the queue's segment limit end up allowing more bios (and segments) to > attach the a request until we finally map it. That also means we > pass the BUG_ON at the beginning of virtio_queue_rq, ultimately causing > memory corruption and a crash. > > If we copy bi_vcnt in __bio_clone_fast, the bios and requests properly > report the number of segments and everything works as expected. > > Originally reported at http://bugzilla.opensuse.org/show_bug.cgi?id=888259
Hi, Jeff,
Did you manage to reproduce this problem with commit 0738854 (blk-merge: fix blk_recount_segments) applied? Or perhaps with commit 200612e (dm table: propagate QUEUE_FLAG_NO_SG_MERGE)?
Cheers, Jeff
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