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%3Ba=su...
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@vger.kernel.org know about it.
From ce8a3a9e76d0193e2e8d74a06d275b3c324ca652 Mon Sep 17 00:00:00 2001
From: Ben Hutchings ben@decadent.org.uk Date: Sun, 4 Feb 2018 02:06:27 +0000 Subject: staging: android: ashmem: Fix a race condition in pin ioctls
From: Ben Hutchings ben@decadent.org.uk
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@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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@decadent.org.uk are
queue-4.4/staging-android-ashmem-fix-a-race-condition-in-pin-ioctls.patch