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Commit 6832a333 authored by David S. Miller's avatar David S. Miller
Browse files

bpf: Handle multiple variable additions into packet pointers in verifier. 



We must accumulate into reg->aux_off rather than use a plain assignment.

Add a test for this situation to test_align.

Reported-by: default avatarAlexei Starovoitov <ast@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 844cf763

kernel/bpf/verifier.c

+1 −1
Original line number Diff line number Diff line
@@ -1531,7 +1531,7 @@ static int check_packet_ptr_add(struct bpf_verifier_env *env, 
		dst_reg->id = ++env->id_gen;



		/* something was added to pkt_ptr, set range to zero */

		dst_reg->aux_off = dst_reg->off;

		dst_reg->aux_off += dst_reg->off;

		dst_reg->off = 0;

		dst_reg->range = 0;

		if (had_id)

tools/testing/selftests/bpf/test_align.c

+37 −0
Original line number Diff line number Diff line
@@ -273,6 +273,20 @@ static struct bpf_align_test tests[] = { 
			BPF_EXIT_INSN(),

			BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_5, 0),



			/* Test multiple accumulations of unknown values

			 * into a packet pointer.

			 */

			BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),

			BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),

			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),

			BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 4),

			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),

			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),

			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),

			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),

			BPF_EXIT_INSN(),

			BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_5, 0),



			BPF_MOV64_IMM(BPF_REG_0, 0),

			BPF_EXIT_INSN(),

		},
@@ -314,6 +328,29 @@ static struct bpf_align_test tests[] = { 
			 * requirements.

			 */

			"23: R0=pkt(id=0,off=8,r=8) R1=ctx R2=pkt(id=0,off=0,r=8) R3=pkt_end R4=pkt(id=2,off=18,r=18),aux_off_align=4 R5=pkt(id=2,off=14,r=18),aux_off_align=4 R6=inv54,min_align=4 R10=fp",



			/* Constant offset is added to R5 packet pointer,

			 * resulting in reg->off value of 14.

			 */

			"26: R0=pkt(id=0,off=8,r=8) R1=ctx R2=pkt(id=0,off=0,r=8) R3=pkt_end R4=inv,aux_off_align=4 R5=pkt(id=0,off=14,r=8) R6=inv54,min_align=4 R10=fp",

			/* Variable offset is added to R5, resulting in an

			 * auxiliary offset of 14, and an auxiliary alignment of 4.

			 */

			"27: R0=pkt(id=0,off=8,r=8) R1=ctx R2=pkt(id=0,off=0,r=8) R3=pkt_end R4=inv,aux_off_align=4 R5=pkt(id=3,off=0,r=0),aux_off=14,aux_off_align=4 R6=inv54,min_align=4 R10=fp",

			/* Constant is added to R5 again, setting reg->off to 4. */

			"28: R0=pkt(id=0,off=8,r=8) R1=ctx R2=pkt(id=0,off=0,r=8) R3=pkt_end R4=inv,aux_off_align=4 R5=pkt(id=3,off=4,r=0),aux_off=14,aux_off_align=4 R6=inv54,min_align=4 R10=fp",

			/* And once more we add a variable, which causes an accumulation

			 * of reg->off into reg->aux_off_align, with resulting value of

			 * 18.  The auxiliary alignment stays at 4.

			 */

			"29: R0=pkt(id=0,off=8,r=8) R1=ctx R2=pkt(id=0,off=0,r=8) R3=pkt_end R4=inv,aux_off_align=4 R5=pkt(id=4,off=0,r=0),aux_off=18,aux_off_align=4 R6=inv54,min_align=4 R10=fp",

			/* At the time the word size load is performed from R5,

			 * it's total offset is NET_IP_ALIGN + reg->off (0) +

			 * reg->aux_off (18) which is 20.  Then the variable offset

			 * is considered using reg->aux_off_align which is 4 and meets

			 * the load's requirements.

			 */

			"33: R0=pkt(id=0,off=8,r=8) R1=ctx R2=pkt(id=0,off=0,r=8) R3=pkt_end R4=pkt(id=4,off=4,r=4),aux_off=18,aux_off_align=4 R5=pkt(id=4,off=0,r=4),aux_off=18,aux_off_align=4 R6=inv54,min_align=4 R10=fp",

		},

	},

};