Syzkaller reports use-after-free at addr_handler in 5.10 stable releases. The problem was fixed in upstream and backported into 5.14, but wasn't applied to 5.10 and lower versions due to a small merge conflict. This patch is a modified version that can be cleanly applied to 5.10 and 5.4 stable branches. Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
