AZL-83630

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

nvmet: move async event work off nvmet-wq

For target nvmetctrlfree() flushes ctrl->asynceventwork. If nvmetctrlfree() runs on nvmet-wq, the flush re-enters workqueue completion for the same worker:-

A. Async event work queued on nvmet-wq (prior to disconnect): nvmetexecuteasyncevent() queuework(nvmetwq, &ctrl->asyncevent_work)

nvmetaddasyncevent() queuework(nvmetwq, &ctrl->asyncevent_work)

B. Full pre-work chain (RDMA CM path): nvmetrdmacmhandler() nvmetrdmaqueuedisconnect() _nvmetrdmaqueuedisconnect() queuework(nvmetwq, &queue->releasework) processonework() lock((wqcompletion)nvmet-wq) <--------- 1st nvmetrdmareleasequeuework()

C. Recursive path (same worker): nvmetrdmareleasequeuework() nvmetrdmafreequeue() nvmetsqdestroy() nvmetctrlput() nvmetctrlfree() flushwork(&ctrl->asynceventwork) _flushwork() touchwqlockdepmap() lock((wqcompletion)nvmet-wq) <--------- 2nd

Lockdep splat:

============================================ WARNING: possible recursive locking detected 6.19.0-rc3nvme+ #14 Tainted: G N

kworker/u192:42/44933 is trying to acquire lock: ffff888118a00948 ((wqcompletion)nvmet-wq){+.+.}-{0:0}, at: touchwqlockdepmap+0x26/0x90

but task is already holding lock: ffff888118a00948 ((wqcompletion)nvmet-wq){+.+.}-{0:0}, at: processone_work+0x53e/0x660

3 locks held by kworker/u192:42/44933: #0: ffff888118a00948 ((wqcompletion)nvmet-wq){+.+.}-{0:0}, at: processonework+0x53e/0x660 #1: ffffc9000e6cbe28 ((workcompletion)(&queue->releasework)){+.+.}-{0:0}, at: processonework+0x1c5/0x660 #2: ffffffff82d4db60 (rcuread_lock){....}-{1:3}, at: _flushwork+0x62/0x530

Workqueue: nvmet-wq nvmetrdmareleasequeuework [nvmet_rdma] Call Trace: _flushwork+0x268/0x530 nvmetctrlfree+0x140/0x310 [nvmet] nvmetcqput+0x74/0x90 [nvmet] nvmetrdmafreequeue+0x23/0xe0 [nvmetrdma] nvmetrdmareleasequeuework+0x19/0x50 [nvmetrdma] processonework+0x206/0x660 workerthread+0x184/0x320 kthread+0x10c/0x240 retfromfork+0x319/0x390

Move async event work to a dedicated nvmet-aen-wq to avoid reentrant flush on nvmet-wq.