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Commit 4923ec0b authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

bpf: simplify verifier register state assignments 



verifier is using the following structure to track the state of registers:
struct reg_state {
    enum bpf_reg_type type;
    union {
        int imm;
        struct bpf_map *map_ptr;
    };
};
and later on in states_equal() does memcmp(&old->regs[i], &cur->regs[i],..)
to find equivalent states.
Throughout the code of verifier there are assignements to 'imm' and 'map_ptr'
fields and it's not obvious that most of the assignments into 'imm' don't
need to clear extra 4 bytes (like mark_reg_unknown_value() does) to make sure
that memcmp doesn't go over junk left from 'map_ptr' assignment.

Simplify the code by converting 'int' into 'long'

Suggested-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ae95d712

kernel/bpf/verifier.c

+2 −4
Original line number Diff line number Diff line
@@ -142,7 +142,7 @@ struct reg_state { 
	enum bpf_reg_type type;

	union {

		/* valid when type == CONST_IMM | PTR_TO_STACK */

		int imm;

		long imm;



		/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |

		 *   PTR_TO_MAP_VALUE_OR_NULL
@@ -263,7 +263,7 @@ static void print_verifier_state(struct verifier_env *env) 
			continue;

		verbose(" R%d=%s", i, reg_type_str[t]);

		if (t == CONST_IMM || t == PTR_TO_STACK)

			verbose("%d", env->cur_state.regs[i].imm);

			verbose("%ld", env->cur_state.regs[i].imm);

		else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||

			 t == PTR_TO_MAP_VALUE_OR_NULL)

			verbose("(ks=%d,vs=%d)",
@@ -480,7 +480,6 @@ static void init_reg_state(struct reg_state *regs) 
	for (i = 0; i < MAX_BPF_REG; i++) {

		regs[i].type = NOT_INIT;

		regs[i].imm = 0;

		regs[i].map_ptr = NULL;

	}



	/* frame pointer */
@@ -495,7 +494,6 @@ static void mark_reg_unknown_value(struct reg_state *regs, u32 regno) 
	BUG_ON(regno >= MAX_BPF_REG);

	regs[regno].type = UNKNOWN_VALUE;

	regs[regno].imm = 0;

	regs[regno].map_ptr = NULL;

}



enum reg_arg_type {