4.4-stable review patch. If anyone has any objections, please let me know.
------------------
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;