nvmet: fix race in nvmet_bio_done() leading to NULL pointer dereference

Overview

In the Linux kernel, the following vulnerability has been resolved:

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.

Affected

• Linux >= 431e58d56fcb5ff1f9eb630724a922e0d2a941df < ee10b06980acca1d46e0fa36d6fb4a9578eab6e4
• Linux >= 190f4c2c863af7cc5bb354b70e0805f06419c038 < 68207ceefd71cc74ce4e983fa9bd10c3122e349b
• Linux >= 190f4c2c863af7cc5bb354b70e0805f06419c038 < 0fcee2cfc4b2e16e62ff8e0cc2cd8dd24efad65e
• Linux 2e2028fcf924d1c6df017033c8d6e28b735a0508
• Linux >= 6.12.37 < 6.12.69
• Linux >= 6.15.6 < 6.16
• Linux 6.16

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.