[PATCH 5.15 08/71] bpf: Generalize check_ctx_reg for reuse with other types

Greg Kroah-Hartman
2024-04-23T21:46:20Z

From: Daniel Borkmann <daniel@iogearbox.net>

commit be80a1d3f9dbe5aee79a325964f7037fe2d92f30 upstream.

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>
Signed-off-by: Edward Liaw <edliaw@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/bpf_verifier.h | 4 ++--
kernel/bpf/btf.c | 2 +-
kernel/bpf/verifier.c | 21 +++++++++++----------
3 files changed, 14 insertions(+), 13 deletions(-)

--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -541,8 +541,8 @@ bpf_prog_offload_replace_insn(struct bpf
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);

--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5558,7 +5558,7 @@ static int btf_check_func_arg_match(stru
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[base_type(reg->type)] && !type_flag(reg->type)))) {
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3980,16 +3980,16 @@ static int get_callee_stack_depth(struct
}
#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;
}

@@ -3997,7 +3997,8 @@ int check_ctx_reg(struct bpf_verifier_en
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;
}

@@ -4447,7 +4448,7 @@ static int check_mem_access(struct bpf_v
return -EACCES;
}

- err = check_ctx_reg(env, reg, regno);
+ err = check_ptr_off_reg(env, reg, regno);
if (err < 0)
return err;

@@ -5327,7 +5328,7 @@ static int check_func_arg(struct bpf_ver
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;
}
@@ -9561,7 +9562,7 @@ static int check_ld_abs(struct bpf_verif
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;