From d71962f3e627b5941804036755c844fabfb65ff5 Mon Sep 17 00:00:00 2001 From: Paul Chaignon Date: Tue, 24 Apr 2018 15:07:54 +0200 Subject: [PATCH] bpf: allow map helpers access to map values directly Helpers that expect ARG_PTR_TO_MAP_KEY and ARG_PTR_TO_MAP_VALUE can only access stack and packet memory. Allow these helpers to directly access map values by passing registers of type PTR_TO_MAP_VALUE. This change removes the need for an extra copy to the stack when using a map value to perform a second map lookup, as in the following: struct bpf_map_def SEC("maps") infobyreq = { .type = BPF_MAP_TYPE_HASHMAP, .key_size = sizeof(struct request *), .value_size = sizeof(struct info_t), .max_entries = 1024, }; struct bpf_map_def SEC("maps") counts = { .type = BPF_MAP_TYPE_HASHMAP, .key_size = sizeof(struct info_t), .value_size = sizeof(u64), .max_entries = 1024, }; SEC("kprobe/blk_account_io_start") int bpf_blk_account_io_start(struct pt_regs *ctx) { struct info_t *info = bpf_map_lookup_elem(&infobyreq, &ctx->di); u64 *count = bpf_map_lookup_elem(&counts, info); (*count)++; } Signed-off-by: Paul Chaignon Signed-off-by: Daniel Borkmann --- kernel/bpf/verifier.c | 24 +++++++----------------- 1 file changed, 7 insertions(+), 17 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 5dd1dcb902bf..eb1a596aebd3 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1914,7 +1914,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, if (arg_type == ARG_PTR_TO_MAP_KEY || arg_type == ARG_PTR_TO_MAP_VALUE) { expected_type = PTR_TO_STACK; - if (!type_is_pkt_pointer(type) && + if (!type_is_pkt_pointer(type) && type != PTR_TO_MAP_VALUE && type != expected_type) goto err_type; } else if (arg_type == ARG_CONST_SIZE || @@ -1966,14 +1966,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, verbose(env, "invalid map_ptr to access map->key\n"); return -EACCES; } - if (type_is_pkt_pointer(type)) - err = check_packet_access(env, regno, reg->off, - meta->map_ptr->key_size, - false); - else - err = check_stack_boundary(env, regno, - meta->map_ptr->key_size, - false, NULL); + err = check_helper_mem_access(env, regno, + meta->map_ptr->key_size, false, + NULL); } else if (arg_type == ARG_PTR_TO_MAP_VALUE) { /* bpf_map_xxx(..., map_ptr, ..., value) call: * check [value, value + map->value_size) validity @@ -1983,14 +1978,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, verbose(env, "invalid map_ptr to access map->value\n"); return -EACCES; } - if (type_is_pkt_pointer(type)) - err = check_packet_access(env, regno, reg->off, - meta->map_ptr->value_size, - false); - else - err = check_stack_boundary(env, regno, - meta->map_ptr->value_size, - false, NULL); + err = check_helper_mem_access(env, regno, + meta->map_ptr->value_size, false, + NULL); } else if (arg_type_is_mem_size(arg_type)) { bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO); -- 2.11.0