From: Keith Busch The data segment gaps the block layer tracks doesn't apply to bio's that don't have data. Skip calculating this to fix a NULL pointer access. Fixes: 2f6b2565d43cdb5 ("block: accumulate memory segment gaps per bio") Reported-by: Matthew Wilcox Signed-off-by: Keith Busch --- block/blk-merge.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/blk-merge.c b/block/blk-merge.c index 3ca6fbf8b7870..d3115d7469df0 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -737,6 +737,9 @@ u8 bio_seg_gap(struct request_queue *q, struct bio *prev, struct bio *next, { struct bio_vec pb, nb; + if (!bio_has_data(prev)) + return 0; + gaps_bit = min_not_zero(gaps_bit, prev->bi_bvec_gap_bit); gaps_bit = min_not_zero(gaps_bit, next->bi_bvec_gap_bit); -- 2.47.3