From 9eaf56f04e3cd78c0ac691fb8b25ee8e81d07023 Mon Sep 17 00:00:00 2001 From: Viktor Slavkovic Date: Mon, 2 Oct 2017 10:26:45 -0700 Subject: [PATCH] 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 Change-Id: Ia52312a75ade30bc94be6b94420f17f34e0c1f86 Signed-off-by: Francisco Franco --- 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 29e889ea6cf3..66d1feea5ce2 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -694,10 +694,12 @@ 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;