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

staging: android: ashmem: fix a race condition in ASHMEM_SET_SIZE ioctl

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: staging-android-ashmem-fix-a-race-condition-in-ashmem_set_size-ioctl.patch and it can be found in the queue-4.4 subdirectory.

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

From 443064cb0b1fb4569fe0a71209da7625129fb760 Mon Sep 17 00:00:00 2001

From: Viktor Slavkovic viktors@google.com Date: Mon, 8 Jan 2018 10:43:03 -0800 Subject: staging: android: ashmem: fix a race condition in ASHMEM_SET_SIZE ioctl

From: Viktor Slavkovic viktors@google.com

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 viktors@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- 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;

Patches currently in stable-queue which might be from viktors@google.com are

queue-4.4/staging-android-ashmem-fix-a-race-condition-in-ashmem_set_size-ioctl.patch