From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f198.google.com (mail-dy1-f198.google.com [74.125.82.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B54725437C3 for ; Wed, 14 Oct 2026 17:39:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791999596; cv=none; b=iLVtV5MBZIL8IqX2gF0AngQcdYhR4Ej3EG9wUpT/bzrY+8uoaHij9rPQHrL0rmLxU6IakZOuJsIvZR1Dtst6N/xdZqOhaEa+dgwDaHh2MW8Q5JFVWvO6yTtR/iLMOWouOspY1rJhNd7Nd3Aoxch+9rh88av/4WTK9+53lTXIh9w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791999596; c=relaxed/simple; bh=YFdQEoWDdeGWa/TWsgMs/pBKXtuXfzL+LdXOVde+pIM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=FAaFNx4stqBAE3J9bh2ljtJuR5y9sRMU7mWjl8M5QtxcUAwy0ltn28B+O0HBKZ9KriWqG5f7KgBkNUnEwmDcWJn3i3Z+mWStqrpOjcRTsUuzx1FyhETXcjBhAmLLD9kUDWnkrsc47wnBsoWXd1DLEJTJ7zKWgteOyLYpUCMEoRM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--almasrymina.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=U6O2az6J; arc=none smtp.client-ip=74.125.82.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--almasrymina.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="U6O2az6J" Received: by mail-dy1-f198.google.com with SMTP id 5a478bee46e88-35cbea41088so1840493eec.1 for ; Wed, 14 Oct 2026 10:39:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1791999590; x=1792604390; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=bRbC+uzuGq379sOHpsPue+EBr06ngtqseW1XBOx8dXc=; b=U6O2az6JuqncanWYwEkDrRdjKPU4OOAb7ei3GlZvr5r58gZ9Qu5E4/XclZhDUUPPtB qdBNF3czkP+O6cShDlE9CtaVVFJTCxDim8izuglett8EH77tfY4+sJHQMavs9Yr75Djc GlDix78WCgnWB+z4GZrNz5BYDttEhNQle4okFHcmW/9c0SYZ23VQyFn6PSTtvLobXbNI hbumZMngexgYXrSxNmn5bJWfLLmzSTLrZ6/v+x48UvvgOIv5ALFJdHig4OKLKQnlP8VN i/YIgPtoUWWWzH4sdGjUVYQxcrndayrZbxvLEb8XlmeD+gi/PBa9ha6pEEqNr+c7/OWV BiIw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791999590; x=1792604390; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=bRbC+uzuGq379sOHpsPue+EBr06ngtqseW1XBOx8dXc=; b=iPO9WB/C8UbpqLcMzgCYT13bvuX6+Zhzm9mXLzBvLGIE/hqy5B0RiDbmF0JSmJYFoC JvjUSwJmzZofT22403uboRvnuRnjoRIeDUInI7WpfOIJhwP2EJ4Qf3u/RstirUSc+l23 2FV1nySjQQdUkI56rusqDuNT3weJwBTqbKZa7EfNi2gV80VBqzU4iRHKB0bCNodejCIR mT/cgO+y+b7GZWMdEdO2egHzJEXOerzODVJpqwXVVCBEjZthoAD4xXKccitC9DGLYJ/G VlqnnXmn1nbIpZaUv/PH6n4pGKsxjVlicG5SKWvwSimkf4P88c8WFEWLgSHTvNivlhsX 9MZw== X-Gm-Message-State: AFq9FYIM+1p3FYLy3QHtVJX5btVDb31wDGk3a1rJzPlRrn4pTCNBfbBm Nwxuphif4c03FsCkdVn2hlEnh/WnZUnwbyKsWrDWwKI74mxHgp8QWgs1yRN8SsgkcCcoXguZZWi vg4blZIRRyLkcG+cr77/QChWZK3CBSh4yzGR79Z/LW40x1nxe1tycoxP8NtOJt1LfIF7PUEsD73 tjIh7pw1fyDPz98S/N8j6FBk6topXxT6ub7g+YYwOiYI/im+Do4rTIygdoKt5M+zE= X-Received: from dycaq4.prod.google.com ([2002:a05:7301:7e04:b0:359:198a:8046]) (user=almasrymina job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7300:f643:b0:35d:4e41:d2c2 with SMTP id 5a478bee46e88-35d4e41d4c4mr5062722eec.33.1791999589085; Wed, 14 Oct 2026 10:39:49 -0700 (PDT) Date: Wed, 14 Oct 2026 17:37:17 +0000 In-Reply-To: <20261014173945.373295-1-almasrymina@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20261014173945.373295-1-almasrymina@google.com> X-Mailer: git-send-email 2.56.0.212.g129ede20d9-goog Message-ID: <20261014173945.373295-4-almasrymina@google.com> Subject: [PATCH net-next v3 3/6] net: skbuff: replace skb_page_unref() and __skb_frag_unref() with skb_netmem_unref() From: Mina Almasry To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org Cc: Mina Almasry , Ayush Sawal , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Tariq Toukan , Simon Horman , Steffen Klassert , Herbert Xu , Neal Cardwell , Kuniyuki Iwashima , John Fastabend , Sabrina Dubroca , Eric Biggers , Kees Cook , Aleksandr Loktionov , Petr Machata , "=?UTF-8?q?Uwe=20Kleine-K=C3=B6nig=20=28The=20Capable=20Hub=29?=" , Jakub Raczynski , Wang Zhan , Willem de Bruijn Content-Type: text/plain; charset="UTF-8" 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. Found by code inspection and confirmed with the KUnit tests added later in this series; not observed in production. The mlx4, sky2, and TLS call-site changes are compile-tested only. Assisted-by: LLM Signed-off-by: Mina Almasry --- v2: - Note how the issue was found and how the change was tested. - Link to v1: https://lore.kernel.org/netdev/20261010083935.3274178-4-almasrymina@google.com/ --- 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 76a42c60508d9..980bbe9166393 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); -- 2.56.0.212.g129ede20d9-goog