[PATCH 5.15.y v3 2/5] bpf: Generalize check_ctx_reg for reuse with other types

[Edward Liaw <edliaw@xxxxxxxxxx>]

From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
(cherry picked from commit be80a1d3f9dbe5aee79a325964f7037fe2d92f30)
Signed-off-by: Edward Liaw <edliaw@xxxxxxxxxx>
---
 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 77929fd7bcef..a0c7e13e0ab4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5558,7 +5558,7 @@ 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[base_type(reg->type)] && !type_flag(reg->type)))) {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 008ddb694c8a..6fe805b559c0 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3980,16 +3980,16 @@ 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;
 	}
 
@@ -3997,7 +3997,8 @@ 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;
 	}
 
@@ -4447,7 +4448,7 @@ 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;
 
@@ -5327,7 +5328,7 @@ 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;
 	}
@@ -9561,7 +9562,7 @@ 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;
 
-- 
2.44.0.769.g3c40516874-goog