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Commit 343f845b authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

x86: bpf_jit: fix FROM_BE16 and FROM_LE16/32 instructions 



FROM_BE16:
'ror %reg, 8' doesn't clear upper bits of the register,
so use additional 'movzwl' insn to zero extend 16 bits into 64

FROM_LE16:
should zero extend lower 16 bits into 64 bit

FROM_LE32:
should zero extend lower 32 bits into 64 bit

Fixes: 89aa0758 ("net: sock: allow eBPF programs to be attached to sockets")
Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e3d8ecb7

arch/x86/net/bpf_jit_comp.c

+28 −0
Original line number Diff line number Diff line
@@ -559,6 +559,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, 
				if (is_ereg(dst_reg))

					EMIT1(0x41);

				EMIT3(0xC1, add_1reg(0xC8, dst_reg), 8);



				/* emit 'movzwl eax, ax' */

				if (is_ereg(dst_reg))

					EMIT3(0x45, 0x0F, 0xB7);

				else

					EMIT2(0x0F, 0xB7);

				EMIT1(add_2reg(0xC0, dst_reg, dst_reg));

				break;

			case 32:

				/* emit 'bswap eax' to swap lower 4 bytes */
@@ -577,6 +584,27 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, 
			break;



		case BPF_ALU | BPF_END | BPF_FROM_LE:

			switch (imm32) {

			case 16:

				/* emit 'movzwl eax, ax' to zero extend 16-bit

				 * into 64 bit

				 */

				if (is_ereg(dst_reg))

					EMIT3(0x45, 0x0F, 0xB7);

				else

					EMIT2(0x0F, 0xB7);

				EMIT1(add_2reg(0xC0, dst_reg, dst_reg));

				break;

			case 32:

				/* emit 'mov eax, eax' to clear upper 32-bits */

				if (is_ereg(dst_reg))

					EMIT1(0x45);

				EMIT2(0x89, add_2reg(0xC0, dst_reg, dst_reg));

				break;

			case 64:

				/* nop */

				break;

			}

			break;



			/* ST: *(u8*)(dst_reg + off) = imm */