From 0fcee2cfc4b2e16e62ff8e0cc2cd8dd24efad65e Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Wed, 21 Jan 2026 17:38:54 +0800 Subject: [PATCH] nvmet: fix race in nvmet_bio_done() leading to NULL pointer dereference There is a race condition in nvmet_bio_done() that can cause a NULL pointer dereference in blk_cgroup_bio_start(): 1. nvmet_bio_done() is called when a bio completes 2. nvmet_req_complete() is called, which invokes req->ops->queue_response(req) 3. The queue_response callback can re-queue and re-submit the same request 4. The re-submission reuses the same inline_bio from nvmet_req 5. Meanwhile, nvmet_req_bio_put() (called after nvmet_req_complete) invokes bio_uninit() for inline_bio, which sets bio->bi_blkg to NULL 6. The re-submitted bio enters submit_bio_noacct_nocheck() 7. blk_cgroup_bio_start() dereferences bio->bi_blkg, causing a crash: BUG: kernel NULL pointer dereference, address: 0000000000000028 #PF: supervisor read access in kernel mode RIP: 0010:blk_cgroup_bio_start+0x10/0xd0 Call Trace: submit_bio_noacct_nocheck+0x44/0x250 nvmet_bdev_execute_rw+0x254/0x370 [nvmet] process_one_work+0x193/0x3c0 worker_thread+0x281/0x3a0 Fix this by reordering nvmet_bio_done() to call nvmet_req_bio_put() BEFORE nvmet_req_complete(). This ensures the bio is cleaned up before the request can be re-submitted, preventing the race condition. Fixes: 190f4c2c863a ("nvmet: fix memory leak of bio integrity") Cc: Dmitry Bogdanov Cc: stable@vger.kernel.org Cc: Guangwu Zhang Link: http://www.mail-archive.com/debian-kernel@lists.debian.org/msg146238.html Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Keith Busch --- drivers/nvme/target/io-cmd-bdev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c index 8d246b8ca604..0103815542d4 100644 --- a/drivers/nvme/target/io-cmd-bdev.c +++ b/drivers/nvme/target/io-cmd-bdev.c @@ -180,9 +180,10 @@ u16 blk_to_nvme_status(struct nvmet_req *req, blk_status_t blk_sts) static void nvmet_bio_done(struct bio *bio) { struct nvmet_req *req = bio->bi_private; + blk_status_t blk_status = bio->bi_status; - nvmet_req_complete(req, blk_to_nvme_status(req, bio->bi_status)); nvmet_req_bio_put(req, bio); + nvmet_req_complete(req, blk_to_nvme_status(req, blk_status)); } #ifdef CONFIG_BLK_DEV_INTEGRITY -- 2.47.3