In the Linux kernel, the following vulnerability has been resolved:
loop: Fix use-after-free issues
doreqfilebacked() calls blkmqcompleterequest() synchronously or asynchronously when using asynchronous I/O unless memory allocation fails. Hence, modify loophandlecmd() such that it does not dereference 'cmd' nor 'rq' after doreq_filebacked() finished unless we are sure that the request has not yet been completed. This patch fixes the following kernel crash:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000054 Call trace: cssput.42938+0x1c/0x1ac loopprocesswork+0xc8c/0xfd4 looprootcgworkfn+0x24/0x34 processonework+0x244/0x558 workerthread+0x400/0x8fc kthread+0x16c/0x1e0 retfromfork+0x10/0x20