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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Andrii Nakryiko , Eduard Zingerman , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, Sechang Lim , Daniel Borkmann , Emil Tsalapatis Subject: [PATCH bpf v3 1/2] bpf, sockmap: settle sk_forward_alloc for strparser SK_PASS Date: Tue, 18 Aug 2026 00:50:08 +0900 Message-ID: <20260817155009.232670-2-zirajs7@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817155009.232670-1-zirajs7@gmail.com> References: <20260817155009.232670-1-zirajs7@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The strparser SK_PASS path can queue cloned skbs back to the same socket. A single TCP receive skb may be split into multiple strparser messages. The strparser clones are unowned, but keep the original truesize. sk_psock_skb_ingress_self() assigns receive ownership with skb_set_owner_r(). That charges each clone to the socket. When this is repeated for strparser clones, sk_forward_alloc can already be in deficit before the next owner assignment. Releasing the queued skbs can then uncharge more memcg pages than were reserved and trigger a page_counter underflow. Fix by making same-socket ingress preserve existing receive ownership and only assign ownership to unowned self-pass skbs. For strparser clones, use a zero-sized sk_rmem_schedule() before skb_set_owner_r() to settle any sk_forward_alloc deficit without reserving the skb's full truesize again. When the skb is retried from the psock backlog, preserve the original _sk_redir value across skb_bpf_redirect_clear() so the deferred path keeps the same ingress and strparser state. Perform the deferred owner assignment under the socket lock because psock backlog work only holds psock->work_mutex. Fixes: 144748eb0c44 ("bpf, sockmap: Fix incorrect fwd_alloc accounting") Reported-by: Sechang Lim Suggested-by: Emil Tsalapatis Assisted-by: Codex:gpt-5.5 Signed-off-by: Junseo Lim --- net/core/skmsg.c | 125 +++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 105 insertions(+), 20 deletions(-) diff --git a/net/core/skmsg.c b/net/core/skmsg.c index 2521b643fa05..347cb168f749 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -586,21 +586,24 @@ static int sk_psock_skb_ingress_enqueue(struct sk_buf= f *skb, } =20 static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buf= f *skb, - u32 off, u32 len, bool take_ref); + u32 off, u32 len, bool take_ref, + bool settle_fwd_alloc); +static int sk_psock_skb_ingress_self_backlog(struct sk_psock *psock, + struct sk_buff *skb, + u32 off, u32 len, bool take_ref, + bool settle_fwd_alloc); =20 static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *sk= b, - u32 off, u32 len) + u32 off, u32 len, bool settle_fwd_alloc) { struct sock *sk =3D psock->sk; struct sk_msg *msg; int err; =20 - /* If we are receiving on the same sock skb->sk is already assigned, - * skip memory accounting and owner transition seeing it already set - * correctly. - */ if (unlikely(skb->sk =3D=3D sk)) - return sk_psock_skb_ingress_self(psock, skb, off, len, true); + return sk_psock_skb_ingress_self_backlog(psock, skb, off, + len, true, + settle_fwd_alloc); msg =3D sk_psock_create_ingress_msg(sk, skb); if (!msg) return -EAGAIN; @@ -618,34 +621,100 @@ static int sk_psock_skb_ingress(struct sk_psock *pso= ck, struct sk_buff *skb, return err; } =20 -/* Puts an skb on the ingress queue of the socket already assigned to the - * skb. In this case we do not need to check memory limits or skb_set_owne= r_r - * because the skb is already accounted for here. +static int sk_psock_skb_ingress_self_assign(struct sock *sk, + struct sk_buff *skb, + bool settle_fwd_alloc) +{ + /* Leave skbs already receive-accounted to sk untouched. */ + if (skb->sk =3D=3D sk && skb->destructor =3D=3D sock_rfree) + return 0; + + if (settle_fwd_alloc) { + sock_owned_by_me(sk); + + if (!sk_rmem_schedule(sk, skb, 0)) + return -EAGAIN; + } + + skb_set_owner_r(skb, sk); + return 0; +} + +/* Puts an skb on the ingress queue for psock->sk. + * + * If the skb already has receive ownership for this socket, leave socket + * memory accounting untouched. Otherwise, before assigning receive owners= hip + * to an unowned strparser SK_PASS skb, settle any existing sk_forward_all= oc + * deficit from earlier clone charges. */ static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buf= f *skb, - u32 off, u32 len, bool take_ref) + u32 off, u32 len, bool take_ref, + bool settle_fwd_alloc) { + struct sock *sk =3D psock->sk; struct sk_msg *msg =3D alloc_sk_msg(GFP_ATOMIC); + int err; + + if (unlikely(!msg)) + return -EAGAIN; + + err =3D sk_psock_skb_ingress_self_assign(sk, skb, settle_fwd_alloc); + if (err) + goto free; + + /* This is used in tcp_bpf_recvmsg_parser() to determine whether the + * data originates from the socket's own protocol stack. No need to + * refcount sk because msg's lifetime is bound to sk via the ingress_msg. + */ + msg->sk =3D sk; + err =3D sk_psock_skb_ingress_enqueue(skb, off, len, psock, sk, msg, + take_ref); + if (err < 0) + goto free; + + return err; +free: + kfree(msg); + return err; +} + +static int sk_psock_skb_ingress_self_backlog(struct sk_psock *psock, + struct sk_buff *skb, + u32 off, u32 len, bool take_ref, + bool settle_fwd_alloc) +{ struct sock *sk =3D psock->sk; + struct sk_msg *msg =3D alloc_sk_msg(GFP_ATOMIC); int err; =20 if (unlikely(!msg)) return -EAGAIN; - skb_set_owner_r(skb, sk); + + lock_sock(sk); + err =3D sk_psock_skb_ingress_self_assign(sk, skb, settle_fwd_alloc); + release_sock(sk); + if (err) + goto free; =20 /* This is used in tcp_bpf_recvmsg_parser() to determine whether the * data originates from the socket's own protocol stack. No need to * refcount sk because msg's lifetime is bound to sk via the ingress_msg. */ msg->sk =3D sk; - err =3D sk_psock_skb_ingress_enqueue(skb, off, len, psock, sk, msg, take_= ref); + err =3D sk_psock_skb_ingress_enqueue(skb, off, len, psock, sk, msg, + take_ref); if (err < 0) - kfree(msg); + goto free; + + return err; +free: + kfree(msg); return err; } =20 static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb, - u32 off, u32 len, bool ingress) + u32 off, u32 len, bool ingress, + bool self_pass, bool strparser) { if (!ingress) { if (!sock_writeable(psock->sk)) @@ -653,7 +722,11 @@ static int sk_psock_handle_skb(struct sk_psock *psock,= struct sk_buff *skb, return skb_send_sock(psock->sk, skb, off, len); } =20 - return sk_psock_skb_ingress(psock, skb, off, len); + if (self_pass) + return sk_psock_skb_ingress_self_backlog(psock, skb, off, + len, true, strparser); + + return sk_psock_skb_ingress(psock, skb, off, len, strparser); } =20 static void sk_psock_skb_state(struct sk_psock *psock, @@ -694,9 +767,14 @@ static void sk_psock_backlog(struct work_struct *work) return; mutex_lock(&psock->work_mutex); while ((skb =3D skb_peek(&psock->ingress_skb))) { + unsigned long saved_redir; + bool strparser; + bool self_pass; + len =3D skb->len; off =3D 0; - if (skb_bpf_strparser(skb)) { + strparser =3D skb_bpf_strparser(skb); + if (strparser) { struct strp_msg *stm =3D strp_msg(skb); =20 off =3D stm->offset; @@ -710,17 +788,20 @@ static void sk_psock_backlog(struct work_struct *work) } =20 ingress =3D skb_bpf_ingress(skb); + self_pass =3D ingress && !skb_bpf_redirect_fetch(skb); + saved_redir =3D skb->_sk_redir; skb_bpf_redirect_clear(skb); do { ret =3D -EIO; if (!sock_flag(psock->sk, SOCK_DEAD)) ret =3D sk_psock_handle_skb(psock, skb, off, - len, ingress); + len, ingress, + self_pass, strparser); if (ret <=3D 0) { if (ret =3D=3D -EAGAIN) { sk_psock_skb_state(psock, state, len, off); /* Restore redir info we cleared before */ - skb_bpf_set_redir(skb, psock->sk, ingress); + skb->_sk_redir =3D saved_redir; /* Delay slightly to prioritize any * other work that might be here. */ @@ -1017,6 +1098,8 @@ static int sk_psock_verdict_apply(struct sk_psock *ps= ock, struct sk_buff *skb, * retrying later from workqueue. */ if (skb_queue_empty(&psock->ingress_skb)) { + bool settle_fwd_alloc =3D false; 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Mon, 17 Aug 2026 08:50:28 -0700 (PDT) Received: from omen-arch ([211.58.239.197]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39339b0d6f4sm4682766a91.0.2026.08.17.08.50.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 08:50:27 -0700 (PDT) From: Junseo Lim To: John Fastabend , Jakub Sitnicki , Jiayuan Chen Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Andrii Nakryiko , Eduard Zingerman , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, Sechang Lim , Daniel Borkmann , Emil Tsalapatis Subject: [PATCH bpf v3 2/2] selftests/bpf: Cover strparser self-pass forward allocation Date: Tue, 18 Aug 2026 00:50:09 +0900 Message-ID: <20260817155009.232670-3-zirajs7@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817155009.232670-1-zirajs7@gmail.com> References: <20260817155009.232670-1-zirajs7@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a sockmap_strp regression test for strparser SK_PASS delivery to the same socket. A one-byte stream parser splits a single write into many messages, repeatedly exercising receive ownership transitions while the skbs remain queued. Verify through INET_DIAG_MEMINFO that sk_forward_alloc does not become negative after the self-pass path is exercised. Signed-off-by: Junseo Lim --- .../selftests/bpf/prog_tests/sockmap_strp.c | 171 ++++++++++++++++++ .../selftests/bpf/progs/test_sockmap_strp.c | 6 + 2 files changed, 177 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_strp.c b/tools/= testing/selftests/bpf/prog_tests/sockmap_strp.c index 1d7231728eaf..c7ad21d0bbf4 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockmap_strp.c +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_strp.c @@ -1,5 +1,9 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include +#include +#include +#include #include #include #include "sockmap_helpers.h" @@ -460,6 +464,171 @@ static void test_sockmap_strp_parser_reject(void) test_sockmap_strp__destroy(strp); } =20 +/* Read sk_forward_alloc through inet_diag meminfo. */ +static int sockmap_strp_get_fwd_alloc(int sock, int *fwd_alloc) +{ + struct sockaddr_storage local =3D {}, peer =3D {}; + struct sockaddr_in *local_in, *peer_in; + socklen_t addr_len =3D sizeof(local); + char buf[1024]; + struct { + struct nlmsghdr nlh; + struct inet_diag_req_v2 req; + } req =3D { + .nlh =3D { + .nlmsg_len =3D sizeof(req), + .nlmsg_type =3D SOCK_DIAG_BY_FAMILY, + .nlmsg_flags =3D NLM_F_REQUEST, + .nlmsg_seq =3D 1, + }, + .req =3D { + .sdiag_family =3D AF_INET, + .sdiag_protocol =3D IPPROTO_TCP, + .idiag_ext =3D 1 << (INET_DIAG_MEMINFO - 1), + .idiag_states =3D ~0U, + .id.idiag_cookie =3D { + INET_DIAG_NOCOOKIE, + INET_DIAG_NOCOOKIE, + }, + }, + }; + int diag_fd, ret, err =3D -ENOENT; + + if (getsockname(sock, (struct sockaddr *)&local, &addr_len)) + return -errno; + addr_len =3D sizeof(peer); + if (getpeername(sock, (struct sockaddr *)&peer, &addr_len)) + return -errno; + + local_in =3D (struct sockaddr_in *)&local; + peer_in =3D (struct sockaddr_in *)&peer; + req.req.id.idiag_sport =3D local_in->sin_port; + req.req.id.idiag_dport =3D peer_in->sin_port; + req.req.id.idiag_src[0] =3D local_in->sin_addr.s_addr; + req.req.id.idiag_dst[0] =3D peer_in->sin_addr.s_addr; + + diag_fd =3D socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, + NETLINK_SOCK_DIAG); + if (diag_fd < 0) + return -errno; + + ret =3D send(diag_fd, &req, sizeof(req), 0); + if (ret < 0) { + err =3D -errno; + goto out; + } + if (ret !=3D sizeof(req)) { + err =3D -EIO; + goto out; + } + + ret =3D recv(diag_fd, buf, sizeof(buf), 0); + if (ret < 0) { + err =3D -errno; + goto out; + } + + for (struct nlmsghdr *nlh =3D (struct nlmsghdr *)buf; + NLMSG_OK(nlh, ret); nlh =3D NLMSG_NEXT(nlh, ret)) { + struct inet_diag_msg *msg =3D NLMSG_DATA(nlh); + struct rtattr *attr; + int len; + + if (nlh->nlmsg_type =3D=3D NLMSG_ERROR) { + err =3D -EINVAL; + goto out; + } + if (nlh->nlmsg_type =3D=3D NLMSG_DONE) + break; + + len =3D nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*msg)); + for (attr =3D (struct rtattr *)(msg + 1); RTA_OK(attr, len); + attr =3D RTA_NEXT(attr, len)) { + struct inet_diag_meminfo *minfo; + + if (attr->rta_type !=3D INET_DIAG_MEMINFO) + continue; + minfo =3D RTA_DATA(attr); + *fwd_alloc =3D (__s32)minfo->idiag_fmem; + err =3D 0; + goto out; + } + } + +out: + close(diag_fd); + return err; +} + +/* Test strparser SK_PASS delivery to the same socket. */ +static void test_sockmap_strp_self_pass_fwd_alloc(void) +{ + struct test_sockmap_strp *strp =3D NULL; + char snd[4 * 1024]; + int c =3D -1, p =3D -1; + int fwd_alloc; + int sndbuf =3D sizeof(snd); + int zero =3D 0; + char rcv; + int sent, recvd; + int map; + int err; + + memset(snd, 0xa5, sizeof(snd)); + + strp =3D test_sockmap_strp__open_and_load(); + if (!ASSERT_OK_PTR(strp, "test_sockmap_strp__open_and_load")) + return; + + map =3D bpf_map__fd(strp->maps.sock_map); + err =3D xbpf_prog_attach(bpf_program__fd(strp->progs.prog_skb_parser_one), + map, BPF_SK_SKB_STREAM_PARSER, 0); + if (err) + goto out_destroy; + + err =3D xbpf_prog_attach(bpf_program__fd(strp->progs.prog_skb_verdict_pas= s), + map, BPF_SK_SKB_STREAM_VERDICT, 0); + if (err) + goto out_destroy; + + err =3D create_pair(AF_INET, SOCK_STREAM, &c, &p); + if (!ASSERT_OK(err, "create_pair")) + goto out_destroy; + + err =3D xsetsockopt(c, SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf)); + if (err) + goto out_destroy; + + err =3D xsetsockopt(p, SOL_SOCKET, SO_RCVBUF, &sndbuf, sizeof(sndbuf)); + if (err) + goto out_destroy; + + err =3D xbpf_map_update_elem(map, &zero, &p, BPF_NOEXIST); + if (err) + goto out_destroy; + + sent =3D send(c, snd, sizeof(snd), MSG_DONTWAIT); + if (!ASSERT_EQ(sent, sizeof(snd), "send")) + goto out_destroy; + + recvd =3D recv_timeout(p, &rcv, sizeof(rcv), MSG_DONTWAIT, + IO_TIMEOUT_SEC); + if (!ASSERT_EQ(recvd, sizeof(rcv), "recv_timeout") || + !ASSERT_EQ(rcv, snd[0], "data mismatch")) + goto out_destroy; + + err =3D sockmap_strp_get_fwd_alloc(p, &fwd_alloc); + if (!ASSERT_OK(err, "sockmap_strp_get_fwd_alloc") || + !ASSERT_GE(fwd_alloc, 0, "sk_forward_alloc")) + goto out_destroy; +out_destroy: + test_sockmap_strp__destroy(strp); + if (c >=3D 0) + close(c); + if (p >=3D 0) + close(p); +} + void test_sockmap_strp(void) { if (test__start_subtest("sockmap strp tcp pass")) @@ -482,4 +651,6 @@ void test_sockmap_strp(void) test_sockmap_strp_dispatch_pkt(AF_INET, SOCK_STREAM); if (test__start_subtest("sockmap strp parser reject pkt mod")) test_sockmap_strp_parser_reject(); + if (test__start_subtest("sockmap strp self pass fwd alloc")) + test_sockmap_strp_self_pass_fwd_alloc(); } diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_strp.c b/tools/= testing/selftests/bpf/progs/test_sockmap_strp.c index fe88fa6d40bc..682e53d40751 100644 --- a/tools/testing/selftests/bpf/progs/test_sockmap_strp.c +++ b/tools/testing/selftests/bpf/progs/test_sockmap_strp.c @@ -50,6 +50,12 @@ int prog_skb_parser_partial(struct __sk_buff *skb) return 10; } =20 +SEC("sk_skb/stream_parser") +int prog_skb_parser_one(struct __sk_buff *skb) +{ + return 1; +} + SEC("sk_skb/stream_parser") int prog_skb_parser_resize(struct __sk_buff *skb) { --=20 2.55.0