From dd8b0582e25e36bba483c60338741c0ba5bc426c Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Mon, 17 Feb 2025 11:16:26 +0800
Subject: [PATCH] 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.
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>
---
block/blk-merge.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 39b738c0e4c9a..c7c85e10cf9cb 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -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,
--
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