From: Zesen Liu Date: Tue, 20 Jan 2026 08:28:47 +0000 (+0800) Subject: bpf: Require ARG_PTR_TO_MEM with memory flag X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ed4724212f6f472fcb529947730ee0ec21c2eb6c;p=thirdparty%2Fkernel%2Flinux.git bpf: Require ARG_PTR_TO_MEM with memory flag Add check to ensure that ARG_PTR_TO_MEM is used with either MEM_WRITE or MEM_RDONLY. Using ARG_PTR_TO_MEM alone without flags does not make sense because: - If the helper does not change the argument, missing MEM_RDONLY causes the verifier to incorrectly reject a read-only buffer. - If the helper does change the argument, missing MEM_WRITE causes the verifier to incorrectly assume the memory is unchanged, leading to errors in code optimization. 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 Reviewed-by: Eduard Zingerman Link: https://lore.kernel.org/r/20260120-helper_proto-v3-2-27b0180b4e77@gmail.com Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index f11dc5366e5b4..bca0ca82d164b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10441,10 +10441,27 @@ static bool check_btf_id_ok(const struct bpf_func_proto *fn) return true; } +static bool check_mem_arg_rw_flag_ok(const struct bpf_func_proto *fn) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) { + enum bpf_arg_type arg_type = fn->arg_type[i]; + + if (base_type(arg_type) != ARG_PTR_TO_MEM) + continue; + if (!(arg_type & (MEM_WRITE | MEM_RDONLY))) + return false; + } + + return true; +} + static int check_func_proto(const struct bpf_func_proto *fn) { return check_raw_mode_ok(fn) && check_arg_pair_ok(fn) && + check_mem_arg_rw_flag_ok(fn) && check_btf_id_ok(fn) ? 0 : -EINVAL; }