Commit 2fb18b5d authored by Alexey Min's avatar Alexey Min 🐧 Committed by Oliver Smith

samsung-klte: backport memfd_create() syscall (!479)

This brings in several patches needed to add support for a
memfd_create() syscall into kernel version 3.4 from kernel
version 3.17. This is required for running lxc >= 3.1.0-r1
with security patch that fixes CVE-2019-5736.

In short, security issue was: in a privileged container root
process could overwrite lxc-start executable by opening its
file descriptor and rewriting executable contents. This is
where memfd comes to help: you can create an in-memory file,
copy your executable there, and place a set of SEALS to protect
it from modifying at a deep level. Then you fexecve() that fd
and you're safe.

For example, pulseaudio also can benefit from having
memfd_create() implemented.

This backports the following commits from upstream linux:
 - dd37978c50bc8b354e5c4633f69387f16572fdac: cache the value
   of file_inode() in struct file

   commit from linux-3.10 to have an f_inode member inside
   struct file and a helper function file_inode() that is
   used in some of the following commits

 - 40e041a2c858b3caefc757e26cb85bfceae5062b shm: add sealing API

   from 3.17: security measure called SEALS, that you can put
   on memfd file to restrict operations on it

 - 9183df25fe7b194563db3fec6dc3202a5855839c shm: add memfd_create()
   syscall

   also from 3.17

 - 503e6636b6f96056210062be703356f4253b6db9 asm-generic: add
   memfd_create system call to unistd.h

 - e57e41931134e09fc6c03c8d4eb19d516cc6e59b ARM: wire up
   memfd_create syscall

The last two are needed to make the syscall visible/usable from
userspace, one in generic context, other for ARM arch.

The test program (https://github.com/minlexx/test_memfd/) was
written to verify that this works.

[ci:skip-build]: already built successfully in CI
parent 17ab67d2
Pipeline #70165131 passed with stages
in 2 minutes and 29 seconds