This is a note to let you know that I've just added the patch titled
staging: android: ashmem: Fix a race condition in pin ioctls
to the 4.4-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-pin-ioctls.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@xxxxxxxxxxxxxxx> know about it.
>From ce8a3a9e76d0193e2e8d74a06d275b3c324ca652 Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Date: Sun, 4 Feb 2018 02:06:27 +0000
Subject: staging: android: ashmem: Fix a race condition in pin ioctls
From: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
commit ce8a3a9e76d0193e2e8d74a06d275b3c324ca652 upstream.
ashmem_pin_unpin() reads asma->file and asma->size before taking the
ashmem_mutex, so it can race with other operations that modify them.
Build-tested only.
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/staging/android/ashmem.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -704,30 +704,32 @@ static int ashmem_pin_unpin(struct ashme
size_t pgstart, pgend;
int ret = -EINVAL;
+ mutex_lock(&ashmem_mutex);
+
if (unlikely(!asma->file))
- return -EINVAL;
+ goto out_unlock;
- if (unlikely(copy_from_user(&pin, p, sizeof(pin))))
- return -EFAULT;
+ if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) {
+ ret = -EFAULT;
+ goto out_unlock;
+ }
/* per custom, you can pass zero for len to mean "everything onward" */
if (!pin.len)
pin.len = PAGE_ALIGN(asma->size) - pin.offset;
if (unlikely((pin.offset | pin.len) & ~PAGE_MASK))
- return -EINVAL;
+ goto out_unlock;
if (unlikely(((__u32)-1) - pin.offset < pin.len))
- return -EINVAL;
+ goto out_unlock;
if (unlikely(PAGE_ALIGN(asma->size) < pin.offset + pin.len))
- return -EINVAL;
+ goto out_unlock;
pgstart = pin.offset / PAGE_SIZE;
pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
- mutex_lock(&ashmem_mutex);
-
switch (cmd) {
case ASHMEM_PIN:
ret = ashmem_pin(asma, pgstart, pgend);
@@ -740,6 +742,7 @@ static int ashmem_pin_unpin(struct ashme
break;
}
+out_unlock:
mutex_unlock(&ashmem_mutex);
return ret;
Patches currently in stable-queue which might be from ben@xxxxxxxxxxxxxxx are
queue-4.4/staging-android-ashmem-fix-a-race-condition-in-pin-ioctls.patch