From b4106c55b574fe37900b02ddf89cbe4b9d971392 Mon Sep 17 00:00:00 2001 From: Viktor Slavkovic Date: Mon, 8 Jan 2018 10:43:03 -0800 Subject: staging: android: ashmem: fix a race condition in ASHMEM_SET_SIZE ioctl commit 443064cb0b1fb4569fe0a71209da7625129fb760 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ashmem.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/staging') diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index 9c6357c03905..b64327722660 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -759,10 +759,12 @@ 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; -- cgit v1.2.3