Unreferencing a page_pool fragment with recycle=false decrements the non-pp backing refcount instead of pp_ref_count, underflowing the page refcount when the fragment was owned via page_pool (as on mlx4's RX error path). Having both skb_page_unref() and __skb_frag_unref(frag, recycle) made it easy for callers to pass hardcoded recycle=false on SKB-owned fragments. Replace skb_page_unref() and __skb_frag_unref() with skb_netmem_unref(netmem, recycle), which dispatches to napi_pp_put_page() when recycle is true and put_netmem() otherwise: - Use skb_frag_unref(skb, ...) on SKB-owned fragments in mlx4, sky2, tls_strp, and skb_shift() so unrefs always match skb->pp_recycle. - Use put_netmem() directly in tls_device's destroy_record(), which releases raw non-pp page references outside an SKB. Signed-off-by: Mina Almasry --- drivers/net/ethernet/marvell/sky2.c | 2 +- drivers/net/ethernet/mellanox/mlx4/en_rx.c | 2 +- include/linux/skbuff_ref.h | 34 +++++++++++----------- net/core/skbuff.c | 7 +++-- net/ipv4/esp4.c | 4 +-- net/ipv6/esp6.c | 4 +-- net/tls/tls_device.c | 2 +- net/tls/tls_strp.c | 2 +- 8 files changed, 29 insertions(+), 28 deletions(-) diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c index 30facdece3e29..1d42a82db8f2b 100644 --- a/drivers/net/ethernet/marvell/sky2.c +++ b/drivers/net/ethernet/marvell/sky2.c @@ -2501,7 +2501,7 @@ static void skb_put_frags(struct sk_buff *skb, unsigned int hdr_space, if (length == 0) { /* don't need this page */ - __skb_frag_unref(frag, false); + skb_frag_unref(skb, i); --skb_shinfo(skb)->nr_frags; } else { size = min(length, (unsigned) PAGE_SIZE); diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c index 96f97fa0f5489..fe18606c2ab55 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c @@ -497,7 +497,7 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv, fail: while (nr > 0) { nr--; - __skb_frag_unref(skb_shinfo(skb)->frags + nr, false); + skb_frag_unref(skb, nr); } return 0; } diff --git a/include/linux/skbuff_ref.h b/include/linux/skbuff_ref.h index 0441c220fdbdf..04114c64dad99 100644 --- a/include/linux/skbuff_ref.h +++ b/include/linux/skbuff_ref.h @@ -36,7 +36,16 @@ static __always_inline void skb_frag_ref(struct sk_buff *skb, int f) bool napi_pp_put_page(netmem_ref netmem); -static __always_inline void skb_page_unref(netmem_ref netmem, bool recycle) +/** + * skb_netmem_unref - release a fragment reference on a netmem + * @netmem: netmem to unreference + * @recycle: whether page_pool recycling is enabled (e.g. skb->pp_recycle) + * + * Drops pp_ref_count via napi_pp_put_page() if @recycle is true and @netmem + * belongs to a page_pool; otherwise drops a non-pp backing reference via + * put_netmem(). Counterpart to skb_netmem_ref(). + */ +static __always_inline void skb_netmem_unref(netmem_ref netmem, bool recycle) { #ifdef CONFIG_PAGE_POOL if (recycle && napi_pp_put_page(netmem)) @@ -46,31 +55,22 @@ static __always_inline void skb_page_unref(netmem_ref netmem, bool recycle) } /** - * __skb_frag_unref - release a reference on a paged fragment. - * @frag: the paged fragment - * @recycle: recycle the page if allocated via page_pool - * - * Releases a reference on the paged fragment @frag - * or recycles the page via the page_pool API. - */ -static __always_inline void __skb_frag_unref(skb_frag_t *frag, bool recycle) -{ - skb_page_unref(skb_frag_netmem(frag), recycle); -} - -/** - * skb_frag_unref - release a reference on a paged fragment of an skb. + * skb_frag_unref - release a reference on a paged fragment of an skb * @skb: the buffer * @f: the fragment offset * - * Releases a reference on the @f'th paged fragment of @skb. + * Drops a reference on the @f'th fragment of @skb via skb_netmem_unref() + * (pp_ref_count if skb->pp_recycle and page_pool-backed, else non-pp + * backing refcount), skipping managed zerocopy fragments. Counterpart to + * skb_frag_ref(). */ static __always_inline void skb_frag_unref(struct sk_buff *skb, int f) { struct skb_shared_info *shinfo = skb_shinfo(skb); if (!skb_zcopy_managed(skb)) - __skb_frag_unref(&shinfo->frags[f], skb->pp_recycle); + skb_netmem_unref(skb_frag_netmem(&shinfo->frags[f]), + skb->pp_recycle); } #endif /* _LINUX_SKBUFF_REF_H */ diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 8a8be746828db..46da61ad1f9eb 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1144,7 +1144,8 @@ static void skb_release_data(struct sk_buff *skb, enum skb_drop_reason reason) } for (i = 0; i < shinfo->nr_frags; i++) - __skb_frag_unref(&shinfo->frags[i], skb->pp_recycle); + skb_netmem_unref(skb_frag_netmem(&shinfo->frags[i]), + skb->pp_recycle); free_head: if (shinfo->frag_list) @@ -1154,7 +1155,7 @@ static void skb_release_data(struct sk_buff *skb, enum skb_drop_reason reason) exit: /* When we clone an SKB we copy the reycling bit. The pp_recycle * bit is only set on the head though, so in order to avoid races - * while trying to recycle fragments on __skb_frag_unref() we need + * while trying to recycle fragments on skb_netmem_unref() we need * to make one SKB responsible for triggering the recycle path. * So disable the recycling bit if an SKB is cloned and we have * additional references to the fragmented part of the SKB. @@ -4412,7 +4413,7 @@ int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen) fragto = &skb_shinfo(tgt)->frags[merge]; skb_frag_size_add(fragto, skb_frag_size(fragfrom)); - __skb_frag_unref(fragfrom, skb->pp_recycle); + skb_frag_unref(skb, 0); } /* Reposition in the original skb */ diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c index e76db5817e78e..ae701561d9f12 100644 --- a/net/ipv4/esp4.c +++ b/net/ipv4/esp4.c @@ -117,8 +117,8 @@ static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb, struct scatterlist *src = already_unref ? esp_req_sg(aead, req) : req->src; for (sg = sg_next(src); sg; sg = sg_next(sg)) - skb_page_unref(page_to_netmem(sg_page(sg)), - skb->pp_recycle); + skb_netmem_unref(page_to_netmem(sg_page(sg)), + skb->pp_recycle); } } diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c index b1c9b36f76dc4..d654f0f442388 100644 --- a/net/ipv6/esp6.c +++ b/net/ipv6/esp6.c @@ -134,8 +134,8 @@ static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb, struct scatterlist *src = already_unref ? esp_req_sg(aead, req) : req->src; for (sg = sg_next(src); sg; sg = sg_next(sg)) - skb_page_unref(page_to_netmem(sg_page(sg)), - skb->pp_recycle); + skb_netmem_unref(page_to_netmem(sg_page(sg)), + skb->pp_recycle); } } diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c index f11d0528fc431..b333a9a72cdae 100644 --- a/net/tls/tls_device.c +++ b/net/tls/tls_device.c @@ -143,7 +143,7 @@ static void destroy_record(struct tls_record_info *record) int i; for (i = 0; i < record->num_frags; i++) - __skb_frag_unref(&record->frags[i], false); + put_netmem(skb_frag_netmem(&record->frags[i])); kfree(record); } diff --git a/net/tls/tls_strp.c b/net/tls/tls_strp.c index 6cc222008d95c..53d3256d0114a 100644 --- a/net/tls/tls_strp.c +++ b/net/tls/tls_strp.c @@ -197,7 +197,7 @@ static void tls_strp_flush_anchor_copy(struct tls_strparser *strp) DEBUG_NET_WARN_ON_ONCE(atomic_read(&shinfo->dataref) != 1); for (i = 0; i < shinfo->nr_frags; i++) - __skb_frag_unref(&shinfo->frags[i], false); + skb_frag_unref(strp->anchor, i); shinfo->nr_frags = 0; if (strp->copy_mode) { kfree_skb_list(shinfo->frag_list); -- 2.56.0.385.gd3acb90ef8-goog