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fork,memcg: alloc_thread_stack_node needs to set tsk->stack
Commit5eed6f1dff
("fork,memcg: fix crash in free_thread_stack on memcg charge fail") 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. Link: http://lkml.kernel.org/r/20190619011450.28048-1-aarcange@redhat.com Fixes:9b6f7e163c
("mm: rework memcg kernel stack accounting") Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Rik van Riel <riel@surriel.com> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -248,7 +248,11 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
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struct page *page = alloc_pages_node(node, THREADINFO_GFP,
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THREAD_SIZE_ORDER);
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return page ? page_address(page) : NULL;
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if (likely(page)) {
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tsk->stack = page_address(page);
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return tsk->stack;
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}
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return NULL;
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#endif
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}
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