c/r: prctl: add PR_SET_MM codes to set up mm_struct entries

When we restore a task we need to set up text, data and data heap sizes
from userspace to the values a task had at checkpoint time.  This patch
adds auxilary prctl codes for that.

While most of them have a statistical nature (their values are involved
into calculation of /proc/<pid>/statm output) the start_brk and brk values
are used to compute an allowed size of program data segment expansion.
Which means an arbitrary changes of this values might be dangerous
operation.  So to restrict access the following requirements applied to
prctl calls:

 - The process has to have CAP_SYS_ADMIN capability granted.
 - For all opcodes except start_brk/brk members an appropriate
   VMA area must exist and should fit certain VMA flags,
   such as:
   - code segment must be executable but not writable;
   - data segment must not be executable.

start_brk/brk values must not intersect with data segment and must not
exceed RLIMIT_DATA resource limit.

Still the main guard is CAP_SYS_ADMIN capability check.

Note the kernel should be compiled with CONFIG_CHECKPOINT_RESTORE support
otherwise these prctl calls will return -EINVAL.

[[email protected]: cache current->mm in a local, saving 200 bytes text]
Signed-off-by: Cyrill Gorcunov <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Andrew Vagin <[email protected]>
Cc: Serge Hallyn <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Vasiliy Kulikov <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions