Commit 1d9b86de authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'bpf-fix-verifier-min-max-handling-in-BPF_SUB' 



Edward Cree says:

====================
bpf: fix verifier min/max handling in BPF_SUB

I managed to come up with a test for the swapped bounds in BPF_SUB, so here
 it is along with a patch that fixes it, separated out from my 'rewrite
 everything' series so it can go to -stable.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 70dba204 9305706c

kernel/bpf/verifier.c

+15 −6
Original line number Diff line number Diff line
@@ -1865,10 +1865,12 @@ static void adjust_reg_min_max_vals(struct bpf_verifier_env *env, 
	 * do our normal operations to the register, we need to set the values

	 * to the min/max since they are undefined.

	 */

	if (opcode != BPF_SUB) {

		if (min_val == BPF_REGISTER_MIN_RANGE)

			dst_reg->min_value = BPF_REGISTER_MIN_RANGE;

		if (max_val == BPF_REGISTER_MAX_RANGE)

			dst_reg->max_value = BPF_REGISTER_MAX_RANGE;

	}



	switch (opcode) {

	case BPF_ADD:
@@ -1879,10 +1881,17 @@ static void adjust_reg_min_max_vals(struct bpf_verifier_env *env, 
		dst_reg->min_align = min(src_align, dst_align);

		break;

	case BPF_SUB:

		/* If one of our values was at the end of our ranges, then the

		 * _opposite_ value in the dst_reg goes to the end of our range.

		 */

		if (min_val == BPF_REGISTER_MIN_RANGE)

			dst_reg->max_value = BPF_REGISTER_MAX_RANGE;

		if (max_val == BPF_REGISTER_MAX_RANGE)

			dst_reg->min_value = BPF_REGISTER_MIN_RANGE;

		if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)

			dst_reg->min_value -= min_val;

			dst_reg->min_value -= max_val;

		if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)

			dst_reg->max_value -= max_val;

			dst_reg->max_value -= min_val;

		dst_reg->min_align = min(src_align, dst_align);

		break;

	case BPF_MUL:

tools/testing/selftests/bpf/test_verifier.c

+28 −0
Original line number Diff line number Diff line
@@ -5980,6 +5980,34 @@ static struct bpf_test tests[] = { 
		.result = REJECT,

		.result_unpriv = REJECT,

	},

	{

		"subtraction bounds (map value)",

		.insns = {

			BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),

			BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),

			BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),

			BPF_LD_MAP_FD(BPF_REG_1, 0),

			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,

				     BPF_FUNC_map_lookup_elem),

			BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 9),

			BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_0, 0),

			BPF_JMP_IMM(BPF_JGT, BPF_REG_1, 0xff, 7),

			BPF_LDX_MEM(BPF_B, BPF_REG_3, BPF_REG_0, 1),

			BPF_JMP_IMM(BPF_JGT, BPF_REG_3, 0xff, 5),

			BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_3),

			BPF_ALU64_IMM(BPF_RSH, BPF_REG_1, 56),

			BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1),

			BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_0, 0),

			BPF_EXIT_INSN(),

			BPF_MOV64_IMM(BPF_REG_0, 0),

			BPF_EXIT_INSN(),

		},

		.fixup_map1 = { 3 },

		.errstr_unpriv = "R0 pointer arithmetic prohibited",

		.errstr = "R0 min value is negative, either use unsigned index or do a if (index >=0) check.",

		.result = REJECT,

		.result_unpriv = REJECT,

	},

};



static int probe_filter_length(const struct bpf_insn *fp)

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