bpf: Determine buf_info inside check_buffer_access()

Instead of determining buf_info string in the caller of check_buffer_access(),
we can determine whether the register type is read-only through
type_is_rdonly_mem() helper inside check_buffer_access() and construct
buf_info, making the code slightly cleaner.

Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/YiWYLnAkEZXBP/gH@syu-laptop

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ec3a7b6..e342642 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4062,9 +4062,9 @@ static int check_buffer_access(struct bpf_verifier_env *env,
                               const struct bpf_reg_state *reg,
                               int regno, int off, int size,
                               bool zero_size_allowed,
-                              const char *buf_info,
                               u32 *max_access)
 {
+       const char *buf_info = type_is_rdonly_mem(reg->type) ? "rdonly" : "rdwr";
        int err;
 
        err = __check_buffer_access(env, buf_info, reg, regno, off, size);
@@ -4576,7 +4576,6 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
                                              value_regno);
        } else if (base_type(reg->type) == PTR_TO_BUF) {
                bool rdonly_mem = type_is_rdonly_mem(reg->type);
-               const char *buf_info;
                u32 *max_access;
 
                if (rdonly_mem) {
@@ -4585,15 +4584,13 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
                                        regno, reg_type_str(env, reg->type));
                                return -EACCES;
                        }
-                       buf_info = "rdonly";
                        max_access = &env->prog->aux->max_rdonly_access;
                } else {
-                       buf_info = "rdwr";
                        max_access = &env->prog->aux->max_rdwr_access;
                }
 
                err = check_buffer_access(env, reg, regno, off, size, false,
-                                         buf_info, max_access);
+                                         max_access);
 
                if (!err && value_regno >= 0 && (rdonly_mem || t == BPF_READ))
                        mark_reg_unknown(env, regs, value_regno);
@@ -4856,7 +4853,6 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
                                   struct bpf_call_arg_meta *meta)
 {
        struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
-       const char *buf_info;
        u32 *max_access;
 
        switch (base_type(reg->type)) {
@@ -4883,15 +4879,13 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
                        if (meta && meta->raw_mode)
                                return -EACCES;
 
-                       buf_info = "rdonly";
                        max_access = &env->prog->aux->max_rdonly_access;
                } else {
-                       buf_info = "rdwr";
                        max_access = &env->prog->aux->max_rdwr_access;
                }
                return check_buffer_access(env, reg, regno, reg->off,
                                           access_size, zero_size_allowed,
-                                          buf_info, max_access);
+                                          max_access);
        case PTR_TO_STACK:
                return check_stack_range_initialized(
                                env,