4.14-stable review patch. If anyone has any objections, please let me know.
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From: Viktor Slavkovic viktors@google.com
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 viktors@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/staging/android/ashmem.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -765,10 +765,12 @@ static long ashmem_ioctl(struct file *fi 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;