Patch "staging: android: ashmem: Fix mmap size validation" has been added to the 4.9-stable tree

gregkh at linuxfoundation.org gregkh at linuxfoundation.org
Sat Sep 29 12:06:40 UTC 2018


This is a note to let you know that I've just added the patch titled

    staging: android: ashmem: Fix mmap size validation

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     staging-android-ashmem-fix-mmap-size-validation.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From foo at baz Sat Sep 29 04:29:21 PDT 2018
From: Alistair Strachan <astrachan at google.com>
Date: Tue, 19 Jun 2018 17:57:35 -0700
Subject: staging: android: ashmem: Fix mmap size validation

From: Alistair Strachan <astrachan at google.com>

[ 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 <tkjos at android.com>
Cc: devel at driverdev.osuosl.org
Cc: linux-kernel at vger.kernel.org
Cc: kernel-team at android.com
Cc: Joel Fernandes <joel at joelfernandes.org>
Signed-off-by: Alistair Strachan <astrachan at google.com>
Acked-by: Joel Fernandes (Google) <joel at joelfernandes.org>
Reviewed-by: Martijn Coenen <maco at android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin at microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/staging/android/ashmem.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -383,6 +383,12 @@ static int ashmem_mmap(struct file *file
 		goto out;
 	}
 
+	/* requested mapping size larger than object size */
+	if (vma->vm_end - vma->vm_start > PAGE_ALIGN(asma->size)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	/* requested protection bits must match our allowed protection mask */
 	if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask, 0)) &
 		     calc_vm_prot_bits(PROT_MASK, 0))) {


Patches currently in stable-queue which might be from astrachan at google.com are

queue-4.9/staging-android-ashmem-fix-mmap-size-validation.patch


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