From: Viktor Slavkovic viktors@google.com
This patch has been added to the 4.1 stable tree. If you have any objections, please let us know.
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[ Upstream commit 443064cb0b1fb4569fe0a71209da7625129fb760 ]
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 Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- 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 7dd6bde4f325..c40bd7fbc210 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -758,10 +758,12 @@ 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;