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 doreqfilebacked() 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 retfrom_fork+0x10/0x20