From: Viktor Slavkovic <viktors@xxxxxxxxxx>
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>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/staging/android/ashmem.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
index 0f695df14c9d..372ce9913e6d 100644
--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -765,10 +765,12 @@ static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
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;
--
2.16.0.rc0.223.g4a4ac83678-goog