From: Daniel Borkmann <daniel@iogearbox.net>
Date: Mon, 10 Jan 2022 14:05:49 +0000
Subject: bpf: Generalize check_ctx_reg for reuse with other types
Patch-mainline: v5.17-rc1
Git-commit: be80a1d3f9dbe5aee79a325964f7037fe2d92f30
References: bsc#1194111 bsc#1194765 CVE-2021-4204 CVE-2022-23222
X-Info: minor adjustment in context of kernel/bpf/btf.c:btf_check_func_arg_match(), no "bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support" 3363bd0cfbb80dfcd25003cd3815b0ad8b68d0ff

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>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 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
@@ -519,8 +519,8 @@ 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
@@ -5686,7 +5686,7 @@ 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[reg->type])) {
 			const struct btf_type *reg_ref_t;
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3973,16 +3973,16 @@ 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;
 	}
 
@@ -3990,7 +3990,8 @@ 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;
 	}
 
@@ -4441,7 +4442,7 @@ 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;
 
@@ -5309,7 +5310,7 @@ 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;
 	}
@@ -9654,7 +9655,7 @@ 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;