[PATCH 5.15.y 2/5] bpf: Generalize check_ctx_reg for reuse with other types

From: Daniel Borkmann daniel@iogearbox.net

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 (cherry picked from commit be80a1d3f9dbe5aee79a325964f7037fe2d92f30) Signed-off-by: Edward Liaw edliaw@google.com --- include/linux/bpf_verifier.h | 4 ++-- kernel/bpf/btf.c | 2 +- kernel/bpf/verifier.c | 21 +++++++++++---------- 3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 3d04b48e502d..c0993b079ab5 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -541,8 +541,8 @@ 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);

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index b02f074363dd..2f6dc3fd06bb 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5553,7 +5553,7 @@ 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; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 1c95d97e7aa5..61b8a9c69b1c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3792,16 +3792,16 @@ 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; }

@@ -3809,7 +3809,8 @@ 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; }

@@ -4260,7 +4261,7 @@ 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;

@@ -5140,7 +5141,7 @@ 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; } @@ -9348,7 +9349,7 @@ 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;