From: Zesen Liu Date: Tue, 20 Jan 2026 08:28:46 +0000 (+0800) Subject: bpf: Fix memory access flags in helper prototypes X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=802eef5afb1865bc5536a5302c068ba2215a1f72;p=thirdparty%2Fkernel%2Flinux.git bpf: Fix memory access flags in helper prototypes After commit 37cce22dbd51 ("bpf: verifier: Refactor helper access type tracking"), the verifier started relying on the access type flags 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 flags. 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. For bpf_get_stack_proto_raw_tp, the original MEM_RDONLY was incorrect since the helper writes to the buffer. Change it to ARG_PTR_TO_UNINIT_MEM which correctly indicates write access to potentially uninitialized memory. 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 flags. 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 Acked-by: Eduard Zingerman Link: https://lore.kernel.org/r/20260120-helper_proto-v3-1-27b0180b4e77@gmail.com Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index f8aa1320e2f7c..4d1af703cfcb2 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/bpf/syscall.c b/kernel/bpf/syscall.c index ecc0929ce4629..3c5c03d43f5f7 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -6451,7 +6451,7 @@ static const struct bpf_func_proto bpf_kallsyms_lookup_name_proto = { .func = bpf_kallsyms_lookup_name, .gpl_only = false, .ret_type = RET_INTEGER, - .arg1_type = ARG_PTR_TO_MEM, + .arg1_type = ARG_PTR_TO_MEM | MEM_RDONLY, .arg2_type = ARG_CONST_SIZE_OR_ZERO, .arg3_type = ARG_ANYTHING, .arg4_type = ARG_PTR_TO_FIXED_SIZE_MEM | MEM_UNINIT | MEM_WRITE | MEM_ALIGNED, diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index f73e08c223b5b..bd15ff62490b0 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 d43df98e1deda..d14401193b01d 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, }; @@ -8008,9 +8008,9 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv4_proto = { .gpl_only = true, /* __cookie_v4_init_sequence() is GPL */ .pkt_access = true, .ret_type = RET_INTEGER, - .arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM, + .arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM | MEM_RDONLY, .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, }; @@ -8040,9 +8040,9 @@ static const struct bpf_func_proto bpf_tcp_raw_gen_syncookie_ipv6_proto = { .gpl_only = true, /* __cookie_v6_init_sequence() is GPL */ .pkt_access = true, .ret_type = RET_INTEGER, - .arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM, + .arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM | MEM_RDONLY, .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, }; @@ -8060,9 +8060,9 @@ static const struct bpf_func_proto bpf_tcp_raw_check_syncookie_ipv4_proto = { .gpl_only = true, /* __cookie_v4_check is GPL */ .pkt_access = true, .ret_type = RET_INTEGER, - .arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM, + .arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM | MEM_RDONLY, .arg1_size = sizeof(struct iphdr), - .arg2_type = ARG_PTR_TO_FIXED_SIZE_MEM, + .arg2_type = ARG_PTR_TO_FIXED_SIZE_MEM | MEM_RDONLY, .arg2_size = sizeof(struct tcphdr), }; @@ -8084,9 +8084,9 @@ static const struct bpf_func_proto bpf_tcp_raw_check_syncookie_ipv6_proto = { .gpl_only = true, /* __cookie_v6_check is GPL */ .pkt_access = true, .ret_type = RET_INTEGER, - .arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM, + .arg1_type = ARG_PTR_TO_FIXED_SIZE_MEM | MEM_RDONLY, .arg1_size = sizeof(struct ipv6hdr), - .arg2_type = ARG_PTR_TO_FIXED_SIZE_MEM, + .arg2_type = ARG_PTR_TO_FIXED_SIZE_MEM | MEM_RDONLY, .arg2_size = sizeof(struct tcphdr), }; #endif /* CONFIG_SYN_COOKIES */