From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 002/127] kcov: fix potential use-after-free in kcov_remote_start Date: Thu, 04 Jun 2020 16:45:51 -0700 Message-ID: <20200604234551.RolHa2uFo%akpm@linux-foundation.org> References: <20200604164523.e15f3177f4b69dcb4f2534a1@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:40780 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726026AbgFDXpx (ORCPT ); Thu, 4 Jun 2020 19:45:53 -0400 In-Reply-To: <20200604164523.e15f3177f4b69dcb4f2534a1@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, andreyknvl@gmail.com, andreyknvl@google.com, dvyukov@google.com, elver@google.com, glider@google.com, gregkh@linuxfoundation.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, stern@rowland.harvard.edu, torvalds@linux-foundation.org From: Andrey Konovalov Subject: kcov: fix potential use-after-free in kcov_remote_start If vmalloc() fails in kcov_remote_start() we'll access remote->kcov without holding kcov_remote_lock, so remote might potentially be freed at that point. Cache kcov pointer in a local variable. Link: http://lkml.kernel.org/r/9d9134359725a965627b7e8f2652069f86f1d1fa.1585233617.git.andreyknvl@google.com Link: http://lkml.kernel.org/r/de0d3d30ff90776a2a509cc34c7c1c7521bda125.1584655448.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Dmitry Vyukov Cc: Alan Stern Cc: Alexander Potapenko Cc: Greg Kroah-Hartman Cc: Marco Elver Cc: Andrey Konovalov Signed-off-by: Andrew Morton --- kernel/kcov.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/kernel/kcov.c~kcov-fix-potential-use-after-free-in-kcov_remote_start +++ a/kernel/kcov.c @@ -748,6 +748,7 @@ static const struct file_operations kcov void kcov_remote_start(u64 handle) { struct kcov_remote *remote; + struct kcov *kcov; void *area; struct task_struct *t; unsigned int size; @@ -774,16 +775,17 @@ void kcov_remote_start(u64 handle) spin_unlock(&kcov_remote_lock); return; } + kcov = remote->kcov; /* Put in kcov_remote_stop(). */ - kcov_get(remote->kcov); - t->kcov = remote->kcov; + kcov_get(kcov); + t->kcov = kcov; /* * Read kcov fields before unlock to prevent races with * KCOV_DISABLE / kcov_remote_reset(). */ - size = remote->kcov->remote_size; - mode = remote->kcov->mode; - sequence = remote->kcov->sequence; + size = kcov->remote_size; + mode = kcov->mode; + sequence = kcov->sequence; area = kcov_remote_area_get(size); spin_unlock(&kcov_remote_lock); @@ -791,7 +793,7 @@ void kcov_remote_start(u64 handle) area = vmalloc(size * sizeof(unsigned long)); if (!area) { t->kcov = NULL; - kcov_put(remote->kcov); + kcov_put(kcov); return; } } _