bpf: fix state equivalence

Commmits 57a09bf ("bpf: Detect identical PTR_TO_MAP_VALUE_OR_NULL registers")
and 4846113 ("bpf: allow access into map value arrays") by themselves
are correct, but in combination they make state equivalence ignore 'id' field
of the register state which can lead to accepting invalid program.

Fixes: 57a09bf ("bpf: Detect identical PTR_TO_MAP_VALUE_OR_NULL registers")
Fixes: 4846113 ("bpf: allow access into map value arrays")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/bpf_verifier.h

@@ -18,13 +18,6 @@
 
 struct bpf_reg_state {
 	enum bpf_reg_type type;
-	/*
-	 * Used to determine if any memory access using this register will
-	 * result in a bad access.
-	 */
-	s64 min_value;
-	u64 max_value;
-	u32 id;
 	union {
 		/* valid when type == CONST_IMM | PTR_TO_STACK | UNKNOWN_VALUE */
 		s64 imm;
@@ -40,6 +33,13 @@ struct bpf_reg_state {
 		 */
 		struct bpf_map *map_ptr;
 	};
+	u32 id;
+	/* Used to determine if any memory access using this register will
+	 * result in a bad access. These two fields must be last.
+	 * See states_equal()
+	 */
+	s64 min_value;
+	u64 max_value;
 };
 
 enum bpf_stack_slot_type {

kernel/bpf/verifier.c

@@ -2528,7 +2528,7 @@ static bool states_equal(struct bpf_verifier_env *env,
 		 * we didn't do a variable access into a map then we are a-ok.
 		 */
 		if (!varlen_map_access &&
-		    rold->type == rcur->type && rold->imm == rcur->imm)
+		    memcmp(rold, rcur, offsetofend(struct bpf_reg_state, id)) == 0)
 			continue;
 
 		/* If we didn't map access then again we don't care about the