CVE-2024-50280

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

dm cache: fix flushing uninitialized delayedwork on cachectr error

An unexpected WARNON from flushwork() may occur when cache creation fails, caused by destroying the uninitialized delayedwork waker in the error path of cachecreate(). For example, the warning appears on the superblock checksum error.

Reproduce steps:

dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524288 linear /dev/sdc 262144" dd if=/dev/urandom of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"

Kernel logs:

(snip) WARNING: CPU: 0 PID: 84 at kernel/workqueue.c:4178 _flushwork+0x5d4/0x890

Fix by pulling out the canceldelayedworksync() from the constructor's error path. This patch doesn't affect the use-after-free fix for concurrent dmresume and dmdestroy (commit 6a459d8edbdb ("dm cache: Fix UAF in destroy()")) as cachedtr is not changed.