Samsung SEND_FILE_WITH_HEADER Use-After-Free

Samsung: UAF via missing locking in SENDFILEWITHHEADER handler in fmtpsamsung.c Tested on a Samsung A50 SM-A505FN, running build "samsung/a50xx/a50:9/PPR1.180610.011/A505FNXXS3ASK9:user/release-keys", security patch level 2019-11-01. Samsung's kernel tree contains two implementations of...