bpf: simplify verifier register state assignments (4923ec0b) · Commits · 戴 / test

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:

Daniel Borkmann <daniel@iogearbox.net> Signed-off-by:

Alexei Starovoitov <ast@kernel.org> Acked-by:

Daniel Borkmann <daniel@iogearbox.net> Signed-off-by:

David S. Miller <davem@davemloft.net>

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 {

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