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    Subject[PATCH] 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
    ---
    Commoner in 2.6.30-rc, but needs fixing in 2.6.28.N and 2.6.29.N too.

    mm/mmap.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- 2.6.30-rc2/mm/mmap.c 2009-04-08 18:20:25.000000000 +0100
    +++ linux/mm/mmap.c 2009-04-16 20:31:17.000000000 +0100
    @@ -1575,7 +1575,7 @@ static int acct_stack_growth(struct vm_a
    * 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 */

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