PD#156601: security: fix security issue CVE-2017-13216

staging: android: ashmem: fix a race condition in ASHMEM_SET_SIZE ioctl 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. Bug: 66954097 Signed-off-by: Viktor Slavkovic <[email protected]> Change-Id: I268225133f96fde0fadd1ec621aafef27d392d65 Signed-off-by: Ao Xu <[email protected]>
wrxtasy · Sep 15, 2018 · 2384ca3 · 2384ca3
1 parent 160e5e6
commit 2384ca3
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
@@ -752,10 +752,12 @@ 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;