From: bsegall@google.com Date: Fri, 7 Apr 2017 23:04:51 +0000 (-0700) Subject: ptrace: fix PTRACE_LISTEN race corrupting task->state X-Git-Tag: v3.2.91~24 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3e8dbd069c401b29f760b69dca571fd091697b80;p=pandora-kernel.git ptrace: fix PTRACE_LISTEN race corrupting task->state commit 5402e97af667e35e54177af8f6575518bf251d51 upstream. In PT_SEIZED + LISTEN mode STOP/CONT signals cause a wakeup against __TASK_TRACED. If this races with the ptrace_unfreeze_traced at the end of a PTRACE_LISTEN, this can wake the task /after/ the check against __TASK_TRACED, but before the reset of state to TASK_TRACED. This causes it to instead clobber TASK_WAKING, allowing a subsequent wakeup against TRACED while the task is still on the rq wake_list, corrupting it. Oleg said: "The kernel can crash or this can lead to other hard-to-debug problems. In short, "task->state = TASK_TRACED" in ptrace_unfreeze_traced() assumes that nobody else can wake it up, but PTRACE_LISTEN breaks the contract. Obviusly it is very wrong to manipulate task->state if this task is already running, or WAKING, or it sleeps again" [akpm@linux-foundation.org: coding-style fixes] Fixes: 9899d11f ("ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL") Link: http://lkml.kernel.org/r/xm26y3vfhmkp.fsf_-_@bsegall-linux.mtv.corp.google.com Signed-off-by: Ben Segall Acked-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed