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[34.86.60.15]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-51eb1c0e085sm1824188e0c.11.2025.02.05.07.24.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Feb 2025 07:24:21 -0800 (PST) Date: Wed, 05 Feb 2025 10:24:21 -0500 From: Willem de Bruijn To: Jason Xing , davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, dsahern@kernel.org, willemdebruijn.kernel@gmail.com, willemb@google.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, horms@kernel.org Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, Jason Xing Message-ID: <67a382a56d206_14e083294ef@willemb.c.googlers.com.notmuch> In-Reply-To: <20250204183024.87508-4-kerneljasonxing@gmail.com> References: <20250204183024.87508-1-kerneljasonxing@gmail.com> <20250204183024.87508-4-kerneljasonxing@gmail.com> Subject: Re: [PATCH bpf-next v8 03/12] bpf: stop unsafely accessing TCP fields in bpf callbacks Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Jason Xing wrote: > The "allow_tcp_access" flag is added to indicate that the callback > site has a tcp_sock locked. > > Applying the new member allow_tcp_access in the existing callbacks > where is_fullsock is set to 1 can stop UDP socket accessing struct > tcp_sock and stop TCP socket without sk lock protecting does the > similar thing, or else it could be catastrophe leading to panic. > > To keep it simple, instead of distinguishing between read and write > access, users aren't allowed all read/write access to the tcp_sock > through the older bpf_sock_ops ctx. The new timestamping callbacks > can use newer helpers to read everything from a sk (e.g. bpf_core_cast), > so nothing is lost. > > Signed-off-by: Jason Xing > --- > include/linux/filter.h | 5 +++++ > include/net/tcp.h | 1 + > net/core/filter.c | 8 ++++---- > net/ipv4/tcp_input.c | 2 ++ > net/ipv4/tcp_output.c | 2 ++ > 5 files changed, 14 insertions(+), 4 deletions(-) > > diff --git a/include/linux/filter.h b/include/linux/filter.h > index a3ea46281595..1569e9f31a8c 100644 > --- a/include/linux/filter.h > +++ b/include/linux/filter.h > @@ -1508,6 +1508,11 @@ struct bpf_sock_ops_kern { > void *skb_data_end; > u8 op; > u8 is_fullsock; > + u8 allow_tcp_access; /* Indicate that the callback site > + * has a tcp_sock locked. Then it > + * would be safe to access struct > + * tcp_sock. > + */ perhaps no need for explicit documentation if the variable name is self documenting: is_locked_tcp_sock > u8 remaining_opt_len; > u64 temp; /* temp and everything after is not > * initialized to 0 before calling > diff --git a/include/net/tcp.h b/include/net/tcp.h > index 5b2b04835688..293047694710 100644 > --- a/include/net/tcp.h > +++ b/include/net/tcp.h > @@ -2649,6 +2649,7 @@ static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args) > memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp)); > if (sk_fullsock(sk)) { > sock_ops.is_fullsock = 1; > + sock_ops.allow_tcp_access = 1; > sock_owned_by_me(sk); > } > > diff --git a/net/core/filter.c b/net/core/filter.c > index 1c6c07507a78..dc0e67c5776a 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -10381,10 +10381,10 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type, > } \ > *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF( \ > struct bpf_sock_ops_kern, \ > - is_fullsock), \ > + allow_tcp_access), \ > fullsock_reg, si->src_reg, \ > offsetof(struct bpf_sock_ops_kern, \ > - is_fullsock)); \ > + allow_tcp_access)); \ > *insn++ = BPF_JMP_IMM(BPF_JEQ, fullsock_reg, 0, jmp); \ > if (si->dst_reg == si->src_reg) \ > *insn++ = BPF_LDX_MEM(BPF_DW, reg, si->src_reg, \ > @@ -10469,10 +10469,10 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type, > temp)); \ > *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF( \ > struct bpf_sock_ops_kern, \ > - is_fullsock), \ > + allow_tcp_access), \ > reg, si->dst_reg, \ > offsetof(struct bpf_sock_ops_kern, \ > - is_fullsock)); \ > + allow_tcp_access)); \ > *insn++ = BPF_JMP_IMM(BPF_JEQ, reg, 0, 2); \ > *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF( \ > struct bpf_sock_ops_kern, sk),\ > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c > index eb82e01da911..77185479ed5e 100644 > --- a/net/ipv4/tcp_input.c > +++ b/net/ipv4/tcp_input.c > @@ -169,6 +169,7 @@ static void bpf_skops_parse_hdr(struct sock *sk, struct sk_buff *skb) > memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp)); > sock_ops.op = BPF_SOCK_OPS_PARSE_HDR_OPT_CB; > sock_ops.is_fullsock = 1; > + sock_ops.allow_tcp_access = 1; > sock_ops.sk = sk; > bpf_skops_init_skb(&sock_ops, skb, tcp_hdrlen(skb)); > > @@ -185,6 +186,7 @@ static void bpf_skops_established(struct sock *sk, int bpf_op, > memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp)); > sock_ops.op = bpf_op; > sock_ops.is_fullsock = 1; > + sock_ops.allow_tcp_access = 1; > sock_ops.sk = sk; > /* sk with TCP_REPAIR_ON does not have skb in tcp_finish_connect */ > if (skb) > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > index 0e5b9a654254..695749807c09 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -522,6 +522,7 @@ static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb, > sock_owned_by_me(sk); > > sock_ops.is_fullsock = 1; > + sock_ops.allow_tcp_access = 1; > sock_ops.sk = sk; > } > > @@ -567,6 +568,7 @@ static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb, > sock_owned_by_me(sk); > > sock_ops.is_fullsock = 1; > + sock_ops.allow_tcp_access = 1; > sock_ops.sk = sk; > } > > -- > 2.43.5 >