4.18-stable review patch. If anyone has any objections, please let me know.
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From: Alistair Strachan astrachan@google.com
[ Upstream commit 8632c614565d0c5fdde527889601c018e97b6384 ]
The ashmem driver did not check that the size/offset of the vma passed to its .mmap() function was not larger than the ashmem object being mapped. This could cause mmap() to succeed, even though accessing parts of the mapping would later fail with a segmentation fault.
Ensure an error is returned by the ashmem_mmap() function if the vma size is larger than the ashmem object size. This enables safer handling of the problem in userspace.
Cc: Todd Kjos tkjos@android.com Cc: devel@driverdev.osuosl.org Cc: linux-kernel@vger.kernel.org Cc: kernel-team@android.com Cc: Joel Fernandes joel@joelfernandes.org Signed-off-by: Alistair Strachan astrachan@google.com Acked-by: Joel Fernandes (Google) joel@joelfernandes.org Reviewed-by: Martijn Coenen maco@android.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/staging/android/ashmem.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -366,6 +366,12 @@ static int ashmem_mmap(struct file *file goto out; }
+ /* requested mapping size larger than object size */ + if (vma->vm_end - vma->vm_start > PAGE_ALIGN(asma->size)) { + ret = -EINVAL; + goto out; + } + /* requested protection bits must match our allowed protection mask */ if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask, 0)) & calc_vm_prot_bits(PROT_MASK, 0))) {