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 4.9-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-a-race-condition-in-ashmem_set_size-ioctl.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@xxxxxxxxxxxxxxx> know about it.
>From 443064cb0b1fb4569fe0a71209da7625129fb760 Mon Sep 17 00:00:00 2001
From: Viktor Slavkovic <viktors@xxxxxxxxxx>
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@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/staging/android/ashmem.c | 2 ++
1 file changed, 2 insertions(+)
--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -774,10 +774,12 @@ 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@xxxxxxxxxx are
queue-4.9/staging-android-ashmem-fix-a-race-condition-in-ashmem_set_size-ioctl.patch