From: Zesen Liu <ftyghome@gmail.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>,
Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
Matt Bobrowski <mattbobrowski@google.com>,
Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
Daniel Xu <dxu@dxuuu.xyz>, Shuah Khan <shuah@kernel.org>
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 <ftyghome@gmail.com>,
Shuran Liu <electronlsr@gmail.com>,
Peili Gao <gplhust955@gmail.com>,
Haoran Ni <haoran.ni.cs@gmail.com>
Subject: [RFC PATCH bpf 1/2] bpf: Fix memory access tags in helper prototypes
Date: Sat, 20 Dec 2025 19:35:04 +0800 [thread overview]
Message-ID: <20251220-helper_proto-v1-1-2206e0d9422d@gmail.com> (raw)
In-Reply-To: <20251220-helper_proto-v1-0-2206e0d9422d@gmail.com>
After commit 37cce22dbd51 ("bpf: verifier: Refactor helper access type tracking"),
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 args").
Fix these prototypes by adding the correct memory access tags.
Fixes: 37cce22dbd51 ("bpf: verifier: Refactor helper access type tracking")
Co-developed-by: Shuran Liu <electronlsr@gmail.com>
Signed-off-by: Shuran Liu <electronlsr@gmail.com>
Co-developed-by: Peili Gao <gplhust955@gmail.com>
Signed-off-by: Peili Gao <gplhust955@gmail.com>
Co-developed-by: Haoran Ni <haoran.ni.cs@gmail.com>
Signed-off-by: Haoran Ni <haoran.ni.cs@gmail.com>
Signed-off-by: Zesen Liu <ftyghome@gmail.com>
---
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 = {
.func = bpf_snprintf,
.gpl_only = true,
.ret_type = RET_INTEGER,
- .arg1_type = ARG_PTR_TO_MEM_OR_NULL,
+ .arg1_type = ARG_PTR_TO_MEM_OR_NULL | MEM_WRITE,
.arg2_type = ARG_CONST_SIZE_OR_ZERO,
.arg3_type = ARG_PTR_TO_CONST_STR,
.arg4_type = 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 = {
.func = bpf_snprintf_btf,
.gpl_only = false,
.ret_type = RET_INTEGER,
- .arg1_type = ARG_PTR_TO_MEM,
+ .arg1_type = ARG_PTR_TO_MEM | MEM_WRITE,
.arg2_type = ARG_CONST_SIZE,
.arg3_type = ARG_PTR_TO_MEM | MEM_RDONLY,
.arg4_type = ARG_CONST_SIZE,
@@ -1526,7 +1526,7 @@ static const struct bpf_func_proto bpf_read_branch_records_proto = {
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
- .arg2_type = ARG_PTR_TO_MEM_OR_NULL,
+ .arg2_type = ARG_PTR_TO_MEM_OR_NULL | MEM_WRITE,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
.arg4_type = ARG_ANYTHING,
};
@@ -1661,7 +1661,7 @@ static const struct bpf_func_proto bpf_get_stack_proto_raw_tp = {
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
- .arg2_type = ARG_PTR_TO_MEM | MEM_RDONLY,
+ .arg2_type = ARG_PTR_TO_UNINIT_MEM,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
.arg4_type = 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 = {
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
- .arg2_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_PTR_TO_MEM | MEM_WRITE,
.arg3_type = ARG_CONST_SIZE,
.arg4_type = ARG_ANYTHING,
};
@@ -6454,7 +6454,7 @@ static const struct bpf_func_proto bpf_skb_fib_lookup_proto = {
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
- .arg2_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_PTR_TO_MEM | MEM_WRITE,
.arg3_type = ARG_CONST_SIZE,
.arg4_type = ARG_ANYTHING,
};
@@ -8010,7 +8010,7 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv4_proto = {
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM,
.arg1_size = sizeof(struct iphdr),
- .arg2_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_PTR_TO_MEM | MEM_RDONLY,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
};
@@ -8042,7 +8042,7 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv6_proto = {
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM,
.arg1_size = sizeof(struct ipv6hdr),
- .arg2_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_PTR_TO_MEM | MEM_RDONLY,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
};
--
2.43.0
next prev parent reply other threads:[~2025-12-20 11:35 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-20 11:35 [RFC bpf PATCH 0/2] bpf: Fix memory access tags in helper prototypes Zesen Liu
2025-12-20 11:35 ` Zesen Liu [this message]
2025-12-22 19:29 ` [RFC PATCH bpf 1/2] " Amery Hung
2025-12-23 3:22 ` Zesen Liu
2025-12-20 11:35 ` [RFC PATCH bpf 2/2] selftests/bpf: add regression tests for snprintf and get_stack helpers Zesen Liu
2025-12-22 19:29 ` [RFC bpf PATCH 0/2] bpf: Fix memory access tags in helper prototypes Amery Hung
2025-12-23 3:15 ` Zesen Liu
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