ashmem: Ensure all memfds have non-executable permissions by default
Currently, memfds are created with executable permissions, meaning that
one can load a binary into a memfd buffer and use fexecve() to run said
binary. This is not desirable for security reasons, and also does not
match with the behavior that the ashmem driver currently supports.
When the ashmem driver is in use, /dev/ashmem* does not have executable
permissions, so fexecve() cannot be used on those buffers. Linux kernels
6.3+ offer MFD_NOEXEC_SEAL as part of the memfd interface, which allows
one to create memfds with non-executable permissions. Furthermore, the
executable permissions cannot be changed on these memfds.
This matches the expected behavior that ashmem provided, so allow memfd
usage only if MFD_NOEXEC_SEAL is supported, and create memfds with
non-executable permissions by default.
Bug: 111903542
Change-Id: Ibb2c2be3c118ead44fc12bcd2b63dcf6f83c9b03
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
1 file changed