On Fri, Feb 07, 2025 at 07:09:39PM -0700, Cheyenne Wills wrote: > While I was setting up to test with linux 6.14-rc1 (under Xen), I ran > into a consistent NULL ptr dereference within __blk_rq_map_sg when > booting the system. > > Using git bisect I was able to narrow down the "bad" commit to: > > block: add a dma mapping iterator (b7175e24d6acf79d9f3af9ce9d3d50de1fa748ec) > > Building a kernel with the parent commit > (2caca8fc7aad9ea9a6ea3ed26ed146b1e5f06fab) using the same .config does > not fail. > > Following is the console log showing the error as well as the Xen > (libvirt) configuration for the guest that I'm using. > > Please let me know if there is any additional information that I can provide. Can you test the following patch? diff --git a/block/blk-merge.c b/block/blk-merge.c index b55c52a42303..1eabde8383fb 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -493,7 +493,7 @@ static bool blk_map_iter_next(struct request *req, return true; } - if (!iter->iter.bi_size) + if (!iter->bio || !iter->iter.bi_size) return false; bv = mp_bvec_iter_bvec(iter->bio->bi_io_vec, iter->iter); @@ -514,7 +514,8 @@ static bool blk_map_iter_next(struct request *req, if (!iter->bio->bi_next) break; iter->bio = iter->bio->bi_next; - iter->iter = iter->bio->bi_iter; + if (iter->bio) + iter->iter = iter->bio->bi_iter; } next = mp_bvec_iter_bvec(iter->bio->bi_io_vec, iter->iter); Thanks, Ming
