From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Viktor Slavkovic Subject: [PATCH 3.18 43/46] staging: android: ashmem: fix a race condition in ASHMEM_SET_SIZE ioctl Date: Mon, 15 Jan 2018 13:33:51 +0100 Message-Id: <20180115123332.619539366@linuxfoundation.org> In-Reply-To: <20180115123327.303455538@linuxfoundation.org> References: <20180115123327.303455538@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Viktor Slavkovic commit 443064cb0b1fb4569fe0a71209da7625129fb760 upstream. A lock-unlock is missing in ASHMEM_SET_SIZE ioctl which can result in a race condition when mmap is called. After the !asma->file check, before setting asma->size, asma->file can be set in mmap. That would result in having different asma->size than the mapped memory size. Combined with ASHMEM_UNPIN ioctl and shrinker invocation, this can result in memory corruption. Signed-off-by: Viktor Slavkovic Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ashmem.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -759,10 +759,12 @@ static long ashmem_ioctl(struct file *fi break; case ASHMEM_SET_SIZE: ret = -EINVAL; + mutex_lock(&ashmem_mutex); if (!asma->file) { ret = 0; asma->size = (size_t) arg; } + mutex_unlock(&ashmem_mutex); break; case ASHMEM_GET_SIZE: ret = asma->size;