From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751205AbeAVIZ0 (ORCPT ); Mon, 22 Jan 2018 03:25:26 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:36749 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751040AbeAVIZZ (ORCPT ); Mon, 22 Jan 2018 03:25:25 -0500 X-Google-Smtp-Source: AH8x226RsY1USHPGEeCFp4+UyyVL6vkeEvxOojSXxx/l4fT889q82MXxXZF5YO7bpgxQh5lgldZpCA== From: Dmitry Vyukov To: akpm@linux-foundation.org Cc: sp3485@columbia.edu, andrew.aday@columbia.edu, Dmitry Vyukov , syzkaller@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] kcov: detect double association with a single task Date: Mon, 22 Jan 2018 09:25:20 +0100 Message-Id: <20180122082520.15716-1-dvyukov@google.com> X-Mailer: git-send-email 2.16.0.rc1.238.g530d649a79-goog Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently KCOV_ENABLE does not check if the current task is already associated with another kcov descriptor. As the result it is possible to associate a single task with more than one kcov descriptor, which later leads to a memory leak of the old descriptor. This relation is really meant to be one-to-one (task has only one back link). Extend validation to detect such misuse. Signed-off-by: Dmitry Vyukov Reported-by: Shankara Pailoor Fixes: 5c9a8750a640 ("kernel: add kcov code coverage") Cc: syzkaller@googlegroups.com Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- kernel/kcov.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/kcov.c b/kernel/kcov.c index 7594c033d98a..2c16f1ab5e10 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -358,7 +358,8 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, */ if (kcov->mode != KCOV_MODE_INIT || !kcov->area) return -EINVAL; - if (kcov->t != NULL) + t = current; + if (kcov->t != NULL || t->kcov != NULL) return -EBUSY; if (arg == KCOV_TRACE_PC) kcov->mode = KCOV_MODE_TRACE_PC; @@ -370,7 +371,6 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, #endif else return -EINVAL; - t = current; /* Cache in task struct for performance. */ t->kcov_size = kcov->size; t->kcov_area = kcov->area; -- 2.16.0.rc1.238.g530d649a79-goog