Description

In the Linux kernel, the following vulnerability has been resolved: block: fix request.queuelist usage in flush Friedrich Weber reported a kernel crash problem and bisected to commit 81ada09cc25e ("blk-flush: reuse rq queuelist in flush state machine"). The root cause is that we use "list_move_tail(&rq->queuelist, pending)" in the PREFLUSH/POSTFLUSH sequences. But rq->queuelist.next == xxx since it's popped out from plug->cached_rq in __blk_mq_alloc_requests_batch(). We don't initialize its queuelist just for this first request, although the queuelist of all later popped requests will be initialized. Fix it by changing to use "list_add_tail(&rq->queuelist, pending)" so rq->queuelist doesn't need to be initialized. It should be ok since rq can't be on any list when PREFLUSH or POSTFLUSH, has no move actually. Please note the commit 81ada09cc25e ("blk-flush: reuse rq queuelist in flush state machine") also has another requirement that no drivers would touch rq->queuelist after blk_mq_end_request() since we will reuse it to add rq to the post-flush pending list in POSTFLUSH. If this is not true, we will have to revert that commit IMHO. This updated version adds "list_del_init(&rq->queuelist)" in flush rq callback since the dm layer may submit request of a weird invalid format (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH), which causes double list_add if without this "list_del_init(&rq->queuelist)". The weird invalid format problem should be fixed in dm layer.

Affected Products 5

References 3

• git.kernel.org https://git.kernel.org/stable/c/87907bd69721a8506618a954d41a1de3040e88aa
  Patch
• git.kernel.org https://git.kernel.org/stable/c/d0321c812d89c5910d8da8e4b10c891c6b96ff70
  Patch
• git.kernel.org https://git.kernel.org/stable/c/fe1e395563ccb051e9dbd8fa99859f5caaad2e71
  Patch

Remediation

• git.kernel.org https://git.kernel.org/stable/c/87907bd69721a8506618a954d41a1de3040e88aa
  Patch
• git.kernel.org https://git.kernel.org/stable/c/d0321c812d89c5910d8da8e4b10c891c6b96ff70
  Patch
• git.kernel.org https://git.kernel.org/stable/c/fe1e395563ccb051e9dbd8fa99859f5caaad2e71
  Patch