mm: pass correct mm when growing stack

Tetsuo Handa reports seeing the WARN_ON(current->mm == NULL) in
security_vm_enough_memory(), when do_execve() is touching the
target mm's stack, to set up its args and environment.

Yes, a UMH_NO_WAIT or UMH_WAIT_PROC call_usermodehelper() spawns
an mm-less kernel thread to do the exec.  And in any case, that
vm_enough_memory check when growing stack ought to be done on the
target mm, not on the execer's mm (though apart from the warning,
it only makes a slight tweak to OVERCOMMIT_NEVER behaviour).

Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 4a38411..3303d1b 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1575,7 +1575,7 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns
         * Overcommit..  This must be the final test, as it will
         * update security statistics.
         */
-       if (security_vm_enough_memory(grow))
+       if (security_vm_enough_memory_mm(mm, grow))
                return -ENOMEM;
 
        /* Ok, everything looks good - let it rip */