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* [PATCH net] page_pool: mask the page->signature before the checking
@ 2021-08-05  1:06 Yunsheng Lin
  2021-08-05  1:50 ` Matthew Wilcox
  0 siblings, 1 reply; 6+ messages in thread
From: Yunsheng Lin @ 2021-08-05  1:06 UTC (permalink / raw)
  To: davem, kuba
  Cc: hawk, ilias.apalodimas, mcroce, willy, alexander.duyck, netdev,
	linux-kernel, linuxarm, chenhao288

As mentioned in commit c07aea3ef4d4 ("mm: add a signature
in struct page"):
"The page->signature field is aliased to page->lru.next and
page->compound_head."

And as the comment in page_is_pfmemalloc():
"lru.next has bit 1 set if the page is allocated from the
pfmemalloc reserves. Callers may simply overwrite it if they
do not need to preserve that information."

The page->signature is or’ed with PP_SIGNATURE when a page is
allocated in page pool, see __page_pool_alloc_pages_slow(),
and page->signature is checked directly with PP_SIGNATURE in
page_pool_return_skb_page(), which might cause resoure leaking
problem for a page from page pool if bit 1 of lru.next is set for
a pfmemalloc page.

As bit 0 is page->compound_head, So mask both bit 0 and 1 before
the checking in page_pool_return_skb_page().

Fixes: 6a5bcd84e886 ("page_pool: Allow drivers to hint on SKB recycling")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
---
 net/core/page_pool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 5e4eb45..33b7dd7 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -634,7 +634,7 @@ bool page_pool_return_skb_page(struct page *page)
 	struct page_pool *pp;
 
 	page = compound_head(page);
-	if (unlikely(page->pp_magic != PP_SIGNATURE))
+	if (unlikely((page->pp_magic & ~0x3UL) != PP_SIGNATURE))
 		return false;
 
 	pp = page->pp;
-- 
2.7.4


^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2021-08-05 14:48 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-08-05  1:06 [PATCH net] page_pool: mask the page->signature before the checking Yunsheng Lin
2021-08-05  1:50 ` Matthew Wilcox
2021-08-05  2:14   ` Yunsheng Lin
2021-08-05  8:54     ` Ilias Apalodimas
2021-08-05  9:31       ` Yunsheng Lin
2021-08-05 14:47         ` Ilias Apalodimas

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