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authorAndrea Arcangeli <aarcange@redhat.com>2019-06-28 12:07:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-06-29 16:43:45 +0800
commit1bf4580e00a248a2c86269125390eb3648e1877c (patch)
tree63f8510d48380fcf5d8133c2270b45501106769d
parent8708e13c6a0600625eea3aebd027c0715a5d2bb2 (diff)
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fork,memcg: alloc_thread_stack_node needs to set tsk->stack
Commit 5eed6f1dff87 ("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: 9b6f7e163cd0 ("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>
-rw-r--r--kernel/fork.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 399aca51ff75..61667909ce83 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -248,7 +248,11 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
struct page *page = alloc_pages_node(node, THREADINFO_GFP,
THREAD_SIZE_ORDER);
- return page ? page_address(page) : NULL;
+ if (likely(page)) {
+ tsk->stack = page_address(page);
+ return tsk->stack;
+ }
+ return NULL;
#endif
}