On Tue, 2019-06-18 at 21:14 -0400, Andrea Arcangeli wrote:
> Commit 5eed6f1dff87bfb5e545935def3843edf42800f2 corrected two
> instances, but there was a third instance of this bug.
>
> Without setting tsk->stack, if memcg_charge_kernel_stack fails, it'll
> execute free_thread_stack() on a dangling pointer.
>
> Enterprise kernels are compiled with VMAP_STACK=y so this isn't
> critical, but custom VMAP_STACK=n builds should have some performance
> advantage, with the drawback of risking to fail fork because
> compaction didn't succeed. So as long as VMAP_STACK=n is a supported
> option it's worth fixing it upstream.
>
> Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting")
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxxx>
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