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Sat, 20 Dec 2025 03:35:49 -0800 (PST) From: Zesen Liu Date: Sat, 20 Dec 2025 19:35:04 +0800 Subject: [RFC PATCH bpf 1/2] bpf: Fix memory access tags in helper prototypes Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251220-helper_proto-v1-1-2206e0d9422d@gmail.com> References: <20251220-helper_proto-v1-0-2206e0d9422d@gmail.com> In-Reply-To: <20251220-helper_proto-v1-0-2206e0d9422d@gmail.com> To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Matt Bobrowski , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Daniel Xu , Shuah Khan Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, Zesen Liu , Shuran Liu , Peili Gao , Haoran Ni X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=4723; i=ftyghome@gmail.com; h=from:subject:message-id; bh=TzPsFbXzEN8yJbx8ENdKQ00Lv+fJ8UDDohHsL3t0pNQ=; b=owGbwMvMwCXWI1/u+8bXqJ3xtFoSQ6ZbF0v7/Qwf330Cdnmb2e2jt0ScOaRnKWfMI7P12AJe7 wZXsf6OUhYGMS4GWTFFlt4fhndXZpobb7NZcBBmDisTyBAGLk4BmIhbDsP/0vAbV95In89d8W2J wHG+n4W9rqGi3yaL3zxxaobcJSbpN4wMO3mD/DolW82Xrd0d9UDy/5ezqW8vb5U9eSH+9KXoabX WnAA= X-Developer-Key: i=ftyghome@gmail.com; a=openpgp; fpr=8DF831DDA9693733B63CA0C18C1F774DEC4D3287 After commit 37cce22dbd51 ("bpf: verifier: Refactor helper access type trac= king"), the verifier started relying on the access type tags in helper function prototypes to perform memory access optimizations. Currently, several helper functions utilizing ARG_PTR_TO_MEM lack the corresponding MEM_RDONLY or MEM_WRITE tags. This omission causes the verifier to incorrectly assume that the buffer contents are unchanged across the helper call. Consequently, the verifier may optimize away subsequent reads based on this wrong assumption, leading to correctness issues. Similar issues were recently addressed for specific helpers in commit ac44dcc788b9 ("bpf: Fix verifier assumptions of bpf_d_path's output buffer") and commit 2eb7648558a7 ("bpf: Specify access type of bpf_sysctl_get_name a= rgs"). Fix these prototypes by adding the correct memory access tags. Fixes: 37cce22dbd51 ("bpf: verifier: Refactor helper access type tracking") Co-developed-by: Shuran Liu Signed-off-by: Shuran Liu Co-developed-by: Peili Gao Signed-off-by: Peili Gao Co-developed-by: Haoran Ni Signed-off-by: Haoran Ni Signed-off-by: Zesen Liu --- kernel/bpf/helpers.c | 2 +- kernel/trace/bpf_trace.c | 6 +++--- net/core/filter.c | 8 ++++---- 3 files changed, 8 insertions(+), 8 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index db72b96f9c8c..f66284f8ec2c 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1077,7 +1077,7 @@ const struct bpf_func_proto bpf_snprintf_proto =3D { .func =3D bpf_snprintf, .gpl_only =3D true, .ret_type =3D RET_INTEGER, - .arg1_type =3D ARG_PTR_TO_MEM_OR_NULL, + .arg1_type =3D ARG_PTR_TO_MEM_OR_NULL | MEM_WRITE, .arg2_type =3D ARG_CONST_SIZE_OR_ZERO, .arg3_type =3D ARG_PTR_TO_CONST_STR, .arg4_type =3D ARG_PTR_TO_MEM | PTR_MAYBE_NULL | MEM_RDONLY, diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index fe28d86f7c35..59c2394981c7 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1022,7 +1022,7 @@ const struct bpf_func_proto bpf_snprintf_btf_proto = =3D { .func =3D bpf_snprintf_btf, .gpl_only =3D false, .ret_type =3D RET_INTEGER, - .arg1_type =3D ARG_PTR_TO_MEM, + .arg1_type =3D ARG_PTR_TO_MEM | MEM_WRITE, .arg2_type =3D ARG_CONST_SIZE, .arg3_type =3D ARG_PTR_TO_MEM | MEM_RDONLY, .arg4_type =3D ARG_CONST_SIZE, @@ -1526,7 +1526,7 @@ static const struct bpf_func_proto bpf_read_branch_re= cords_proto =3D { .gpl_only =3D true, .ret_type =3D RET_INTEGER, .arg1_type =3D ARG_PTR_TO_CTX, - .arg2_type =3D ARG_PTR_TO_MEM_OR_NULL, + .arg2_type =3D ARG_PTR_TO_MEM_OR_NULL | MEM_WRITE, .arg3_type =3D ARG_CONST_SIZE_OR_ZERO, .arg4_type =3D ARG_ANYTHING, }; @@ -1661,7 +1661,7 @@ static const struct bpf_func_proto bpf_get_stack_prot= o_raw_tp =3D { .gpl_only =3D true, .ret_type =3D RET_INTEGER, .arg1_type =3D ARG_PTR_TO_CTX, - .arg2_type =3D ARG_PTR_TO_MEM | MEM_RDONLY, + .arg2_type =3D ARG_PTR_TO_UNINIT_MEM, .arg3_type =3D ARG_CONST_SIZE_OR_ZERO, .arg4_type =3D ARG_ANYTHING, }; diff --git a/net/core/filter.c b/net/core/filter.c index 616e0520a0bb..6e07bb994aa7 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6399,7 +6399,7 @@ static const struct bpf_func_proto bpf_xdp_fib_lookup= _proto =3D { .gpl_only =3D true, .ret_type =3D RET_INTEGER, .arg1_type =3D ARG_PTR_TO_CTX, - .arg2_type =3D ARG_PTR_TO_MEM, + .arg2_type =3D ARG_PTR_TO_MEM | MEM_WRITE, .arg3_type =3D ARG_CONST_SIZE, .arg4_type =3D ARG_ANYTHING, }; @@ -6454,7 +6454,7 @@ static const struct bpf_func_proto bpf_skb_fib_lookup= _proto =3D { .gpl_only =3D true, .ret_type =3D RET_INTEGER, .arg1_type =3D ARG_PTR_TO_CTX, - .arg2_type =3D ARG_PTR_TO_MEM, + .arg2_type =3D ARG_PTR_TO_MEM | MEM_WRITE, .arg3_type =3D ARG_CONST_SIZE, .arg4_type =3D ARG_ANYTHING, }; @@ -8010,7 +8010,7 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_sy= ncookie_ipv4_proto =3D { .ret_type =3D RET_INTEGER, .arg1_type =3D ARG_PTR_TO_FIXED_SIZE_MEM, .arg1_size =3D sizeof(struct iphdr), - .arg2_type =3D ARG_PTR_TO_MEM, + .arg2_type =3D ARG_PTR_TO_MEM | MEM_RDONLY, .arg3_type =3D ARG_CONST_SIZE_OR_ZERO, }; =20 @@ -8042,7 +8042,7 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_sy= ncookie_ipv6_proto =3D { .ret_type =3D RET_INTEGER, .arg1_type =3D ARG_PTR_TO_FIXED_SIZE_MEM, .arg1_size =3D sizeof(struct ipv6hdr), - .arg2_type =3D ARG_PTR_TO_MEM, + .arg2_type =3D ARG_PTR_TO_MEM | MEM_RDONLY, .arg3_type =3D ARG_CONST_SIZE_OR_ZERO, }; =20 --=20 2.43.0