Revert "net: mirror skb frag ref/unref helpers"

This reverts commit a580ea994fd37f4105028f5a85c38ff6508a2b25.

This revert is to resolve Dragos's report of page_pool leak here:
https://lore.kernel.org/lkml/20240424165646.1625690-2-dtatulea@nvidia.com/

The reverted patch interacts very badly with commit 2cc3aeb5eccc ("skbuff:
Fix a potential race while recycling page_pool packets"). The reverted
commit hopes that the pp_recycle + is_pp_page variables do not change
between the skb_frag_ref and skb_frag_unref operation. If such a change
occurs, the skb_frag_ref/unref will not operate on the same reference type.
In the case of Dragos's report, the grabbed ref was a pp ref, but the unref
was a page ref, because the pp_recycle setting on the skb was changed.

Attempting to fix this issue on the fly is risky. Lets revert and I hope
to reland this with better understanding and testing to ensure we don't
regress some edge case while streamlining skb reffing.

Fixes: a580ea994fd3 ("net: mirror skb frag ref/unref helpers")
Reported-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://lore.kernel.org/r/20240502175423.2456544-1-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 4 insertions, 35 deletions

diff --git a/include/linux/skbuff_ref.h b/include/linux/skbuff_ref.h
index 4dcdbe9fbc5f..11f0a4063403 100644
--- a/include/linux/skbuff_ref.h
+++ b/include/linux/skbuff_ref.h
@@ -8,47 +8,16 @@
 #define _LINUX_SKBUFF_REF_H
 
 #include <linux/skbuff.h>
-#include <net/page_pool/helpers.h>
-
-#ifdef CONFIG_PAGE_POOL
-static inline bool is_pp_page(struct page *page)
-{
-	return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
-}
-
-static inline bool napi_pp_get_page(struct page *page)
-{
-	page = compound_head(page);
-
-	if (!is_pp_page(page))
-		return false;
-
-	page_pool_ref_page(page);
-	return true;
-}
-#endif
-
-static inline void skb_page_ref(struct page *page, bool recycle)
-{
-#ifdef CONFIG_PAGE_POOL
-	if (recycle && napi_pp_get_page(page))
-		return;
-#endif
-	get_page(page);
-}
 
 /**
  * __skb_frag_ref - take an addition reference on a paged fragment.
  * @frag: the paged fragment
- * @recycle: skb->pp_recycle param of the parent skb. False if no parent skb.
  *
- * Takes an additional reference on the paged fragment @frag. Obtains the
- * correct reference count depending on whether skb->pp_recycle is set and
- * whether the frag is a page pool frag.
+ * Takes an additional reference on the paged fragment @frag.
  */
-static inline void __skb_frag_ref(skb_frag_t *frag, bool recycle)
+static inline void __skb_frag_ref(skb_frag_t *frag)
 {
-	skb_page_ref(skb_frag_page(frag), recycle);
+	get_page(skb_frag_page(frag));
 }
 
 /**
@@ -60,7 +29,7 @@ static inline void __skb_frag_ref(skb_frag_t *frag, bool recycle)
  */
 static inline void skb_frag_ref(struct sk_buff *skb, int f)
 {
-	__skb_frag_ref(&skb_shinfo(skb)->frags[f], skb->pp_recycle);
+	__skb_frag_ref(&skb_shinfo(skb)->frags[f]);
 }
 
 bool napi_pp_put_page(struct page *page);