CVE-2022-49256

In the Linux kernel, the following vulnerability has been resolved: watch_queue: Actually free the watch free_watch() does everything barring actually freeing the watch object. Fix this by adding the missing kfree. kmemleak produces a report something like the following. Note that as an address can be seen in the first word, the watch would appear to have gone through call_rcu(). BUG: memory leak unreferenced object 0xffff88810ce4a200 (size 96): comm "syz-executor352", pid 3605, jiffies 4294947473 (age 13.720s) hex dump (first 32 bytes): e0 82 48 0d 81 88 ff ff 00 00 00 00 00 00 00 00 ..H............. 80 a2 e4 0c 81 88 ff ff 00 00 00 00 00 00 00 00 ................ backtrace: [ ] kmalloc include/linux/slab.h:581 [inline] [ ] kzalloc include/linux/slab.h:714 [inline] [ ] keyctl_watch_key+0xec/0x2e0 security/keys/keyctl.c:1800 [ ] __do_sys_keyctl+0x3c4/0x490 security/keys/keyctl.c:2016 [ ] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [ ] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 [ ] entry_SYSCALL_64_after_hwframe+0x44/0xae