UPSTREAM: block: fix NULL pointer dereferenced within __blk_rq_map_sg
The block layer internal flush request may not have bio attached, so the request iterator has to be initialized from valid req->bio, otherwise NULL pointer dereferenced is triggered. Bug: 399192075 Change-Id: I1485a140849909291ea61648b4a68870032aabef Signed-off-by: Sandeep Dhavale <dhavale@google.com> Cc: Christoph Hellwig <hch@lst.de> Reported-and-tested-by: Cheyenne Wills <cheyenne.wills@gmail.com> Fixes: b7175e24d6ac ("block: add a dma mapping iterator") Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20250217031626.461977-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk> (cherry picked from commit dd8b0582e25e36bba483c60338741c0ba5bc426c) Signed-off-by: Sandeep Dhavale <dhavale@google.com>
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@@ -553,11 +553,14 @@ int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
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{
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struct req_iterator iter = {
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.bio = rq->bio,
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.iter = rq->bio->bi_iter,
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};
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struct phys_vec vec;
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int nsegs = 0;
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/* the internal flush request may not have bio attached */
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if (iter.bio)
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iter.iter = iter.bio->bi_iter;
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while (blk_map_iter_next(rq, &iter, &vec)) {
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*last_sg = blk_next_sg(last_sg, sglist);
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sg_set_page(*last_sg, phys_to_page(vec.paddr), vec.len,
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