From bd2df8dc72201f626d66ca97f2afc8b7f2740713 Mon Sep 17 00:00:00 2001 From: Jackie Liu Date: Wed, 15 Jul 2026 15:35:18 +0800 Subject: [PATCH] block: free copied pages when blk_rq_map_kern() fails bio_copy_kern() allocates pages that are normally freed by the bio completion callback. If blk_rq_append_bio() rejects the bio, however, blk_rq_map_kern() only drops the bio reference. Since bio_put() does not free pages referenced by the bio vectors, those pages leak. This can happen when the bio exceeds the queue segment constraints or when a later mapping cannot be merged into a request built by earlier calls. Track whether the buffer was copied and free those pages before dropping the rejected bio. Fixes: 3a5a39276d2a ("block: allow blk_rq_map_kern to append to requests") Assisted-by: Codex:gpt-5.6-sol Signed-off-by: Jackie Liu Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260715073518.96042-1-liu.yun@linux.dev Signed-off-by: Jens Axboe --- block/blk-map.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/block/blk-map.c b/block/blk-map.c index 768549f19f97..d1d6bbe0ecf1 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -653,6 +653,7 @@ int blk_rq_map_kern(struct request *rq, void *kbuf, unsigned int len, gfp_t gfp_mask) { unsigned long addr = (unsigned long) kbuf; + bool do_copy; struct bio *bio; int ret; @@ -661,7 +662,8 @@ int blk_rq_map_kern(struct request *rq, void *kbuf, unsigned int len, if (!len || !kbuf) return -EINVAL; - if (!blk_rq_aligned(rq->q, addr, len) || object_is_on_stack(kbuf)) + do_copy = !blk_rq_aligned(rq->q, addr, len) || object_is_on_stack(kbuf); + if (do_copy) bio = bio_copy_kern(rq, kbuf, len, gfp_mask); else bio = bio_map_kern(rq, kbuf, len, gfp_mask); @@ -670,8 +672,11 @@ int blk_rq_map_kern(struct request *rq, void *kbuf, unsigned int len, return PTR_ERR(bio); ret = blk_rq_append_bio(rq, bio); - if (unlikely(ret)) + if (unlikely(ret)) { + if (do_copy) + bio_free_pages(bio); blk_mq_map_bio_put(bio); + } return ret; } EXPORT_SYMBOL(blk_rq_map_kern);