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block: fix NULL pointer dereferenced within __blk_rq_map_sg

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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.

Cc: Christoph Hellwig <hch@lst.de>
Reported-and-tested-by: Cheyenne Wills <cheyenne.wills@gmail.com>
Fixes: b7175e24d6 ("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>
This commit is contained in:
Ming Lei 2025-02-17 11:16:26 +08:00 • committed by Jens Axboe
parent 43c70b1040
commit dd8b0582e2
1 changed files with 4 additions and 1 deletions
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5
block/blk-merge.c
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@ -556,11 +556,14 @@ int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
{
struct req_iterator iter = {
.bio = rq->bio,
.iter = rq->bio->bi_iter,
};
struct phys_vec vec;
int nsegs = 0;
/* the internal flush request may not have bio attached */
if (iter.bio)
iter.iter = iter.bio->bi_iter;
while (blk_map_iter_next(rq, &iter, &vec)) {
*last_sg = blk_next_sg(last_sg, sglist);
sg_set_page(*last_sg, phys_to_page(vec.paddr), vec.len,