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bpf: Generalize check_ctx_reg for reuse with other types 

Generalize the check_ctx_reg() helper function into a more generic named one
so that it can be reused for other register types as well to check whether
their offset is non-zero. No functional change.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2022-01-10 14:05:49 +00:00
parent 343e53754b
commit be80a1d3f9
3 changed files with 14 additions and 13 deletions
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4
include/linux/bpf_verifier.h
View File

@ -519,8 +519,8 @@ bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
void
bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
int check_ctx_reg(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno);
int check_ptr_off_reg(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno);
int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
u32 regno, u32 mem_size);

2
kernel/bpf/btf.c
View File

@ -5686,7 +5686,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
i, btf_type_str(t));
return -EINVAL;
}
if (check_ctx_reg(env, reg, regno))
if (check_ptr_off_reg(env, reg, regno))
return -EINVAL;
} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || reg2btf_ids[reg->type])) {
const struct btf_type *reg_ref_t;

21
kernel/bpf/verifier.c
View File

@ -3969,16 +3969,16 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
}
#endif
int check_ctx_reg(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno)
int check_ptr_off_reg(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno)
{
/* Access to ctx or passing it to a helper is only allowed in
* its original, unmodified form.
/* Access to this pointer-typed register or passing it to a helper
* is only allowed in its original, unmodified form.
*/
if (reg->off) {
verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n",
regno, reg->off);
verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
reg_type_str(env, reg->type), regno, reg->off);
return -EACCES;
}
@ -3986,7 +3986,8 @@ int check_ctx_reg(struct bpf_verifier_env *env,
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, "variable ctx access var_off=%s disallowed\n", tn_buf);
verbose(env, "variable %s access var_off=%s disallowed\n",
reg_type_str(env, reg->type), tn_buf);
return -EACCES;
}
@ -4437,7 +4438,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
return -EACCES;
}
err = check_ctx_reg(env, reg, regno);
err = check_ptr_off_reg(env, reg, regno);
if (err < 0)
return err;
@ -5305,7 +5306,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
return err;
if (type == PTR_TO_CTX) {
err = check_ctx_reg(env, reg, regno);
err = check_ptr_off_reg(env, reg, regno);
if (err < 0)
return err;
}
@ -9651,7 +9652,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
return err;
}
err = check_ctx_reg(env, &regs[ctx_reg], ctx_reg);
err = check_ptr_off_reg(env, &regs[ctx_reg], ctx_reg);
if (err < 0)
return err;