From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Sasha Levin To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Alistair Strachan , Todd Kjos , "devel@driverdev.osuosl.org" , "kernel-team@android.com" , Joel Fernandes , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH AUTOSEL 4.4 28/43] staging: android: ashmem: Fix mmap size validation Date: Mon, 17 Sep 2018 03:05:06 +0000 Message-ID: <20180917030445.484-28-alexander.levin@microsoft.com> References: <20180917030445.484-1-alexander.levin@microsoft.com> In-Reply-To: <20180917030445.484-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: From: Alistair Strachan [ Upstream commit 8632c614565d0c5fdde527889601c018e97b6384 ] The ashmem driver did not check that the size/offset of the vma passed to its .mmap() function was not larger than the ashmem object being mapped. This could cause mmap() to succeed, even though accessing parts of the mapping would later fail with a segmentation fault. Ensure an error is returned by the ashmem_mmap() function if the vma size is larger than the ashmem object size. This enables safer handling of the problem in userspace. Cc: Todd Kjos Cc: devel@driverdev.osuosl.org Cc: linux-kernel@vger.kernel.org Cc: kernel-team@android.com Cc: Joel Fernandes Signed-off-by: Alistair Strachan Acked-by: Joel Fernandes (Google) Reviewed-by: Martijn Coenen Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/staging/android/ashmem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ash= mem.c index 013b33760639..e9c74c41aece 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -370,6 +370,12 @@ static int ashmem_mmap(struct file *file, struct vm_ar= ea_struct *vma) goto out; } =20 + /* requested mapping size larger than object size */ + if (vma->vm_end - vma->vm_start > PAGE_ALIGN(asma->size)) { + ret =3D -EINVAL; + goto out; + } + /* requested protection bits must match our allowed protection mask */ if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask)) & calc_vm_prot_bits(PROT_MASK))) { --=20 2.17.1