c/r: prctl: update prctl_set_mm_exe_file() after mm->num_exe_file_vmas removal

A fix for commit b32dfe377102 ("c/r: prctl: add ability to set new
mm_struct::exe_file").

After removing mm->num_exe_file_vmas kernel keeps mm->exe_file until
final mmput(), it never becomes NULL while task is alive.

We can check for other mapped files in mm instead of checking
mm->num_exe_file_vmas, and mark mm with flag MMF_EXE_FILE_CHANGED in
order to forbid second changing of mm->exe_file.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6029d8c54476..c688d4cc2e40 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -439,6 +439,7 @@ extern int get_dumpable(struct mm_struct *mm);
                                         /* leave room for more dump flags */
 #define MMF_VM_MERGEABLE        16      /* KSM may merge identical pages */
 #define MMF_VM_HUGEPAGE         17      /* set when VM_HUGEPAGE is set on vma */
+#define MMF_EXE_FILE_CHANGED    18      /* see prctl_set_mm_exe_file() */
 
 #define MMF_INIT_MASK           (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK)