diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 48 |
1 files changed, 31 insertions, 17 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d6403b5..cced0c1 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1617,6 +1617,30 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env, } #endif +static int check_ctx_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. + */ + + if (reg->off) { + verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n", + regno, reg->off); + return -EACCES; + } + + if (!tnum_is_const(reg->var_off) || reg->var_off.value) { + 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); + return -EACCES; + } + + return 0; +} + /* truncate register to smaller size (in bytes) * must be called with size < BPF_REG_SIZE */ @@ -1686,24 +1710,11 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn verbose(env, "R%d leaks addr into ctx\n", value_regno); return -EACCES; } - /* ctx accesses must be at a fixed offset, so that we can - * determine what type of data were returned. - */ - if (reg->off) { - verbose(env, - "dereference of modified ctx ptr R%d off=%d+%d, ctx+const is allowed, ctx+const+const is not\n", - regno, reg->off, off - reg->off); - return -EACCES; - } - if (!tnum_is_const(reg->var_off) || reg->var_off.value) { - char tn_buf[48]; - tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); - verbose(env, - "variable ctx access var_off=%s off=%d size=%d", - tn_buf, off, size); - return -EACCES; - } + err = check_ctx_reg(env, reg, regno); + if (err < 0) + return err; + err = check_ctx_access(env, insn_idx, off, size, t, ®_type); if (!err && t == BPF_READ && value_regno >= 0) { /* ctx access returns either a scalar, or a @@ -1984,6 +1995,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, expected_type = PTR_TO_CTX; if (type != expected_type) goto err_type; + err = check_ctx_reg(env, reg, regno); + if (err < 0) + return err; } else if (arg_type_is_mem_ptr(arg_type)) { expected_type = PTR_TO_STACK; /* One exception here. In case function allows for NULL to be |
