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Commit d63903bb authored by Xi Wang's avatar Xi Wang Committed by Catalin Marinas
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arm64: bpf: fix endianness conversion bugs 



Upper bits should be zeroed in endianness conversion:

- even when there's no need to change endianness (i.e., BPF_FROM_BE
  on big endian or BPF_FROM_LE on little endian);

- after rev16.

This patch fixes such bugs by emitting extra instructions to clear
upper bits.

Cc: Zi Shen Lim <zlim.lnx@gmail.com>
Acked-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Fixes: e54bcde3 ("arm64: eBPF JIT compiler")
Cc: <stable@vger.kernel.org> # 3.18+
Signed-off-by: default avatarXi Wang <xi.wang@gmail.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 8eee539d

arch/arm64/net/bpf_jit.h

+4 −0
Original line number Diff line number Diff line
@@ -110,6 +110,10 @@ 
/* Rd = Rn >> shift; signed */

#define A64_ASR(sf, Rd, Rn, shift) A64_SBFM(sf, Rd, Rn, shift, (sf) ? 63 : 31)



/* Zero extend */

#define A64_UXTH(sf, Rd, Rn) A64_UBFM(sf, Rd, Rn, 0, 15)

#define A64_UXTW(sf, Rd, Rn) A64_UBFM(sf, Rd, Rn, 0, 31)



/* Move wide (immediate) */

#define A64_MOVEW(sf, Rd, imm16, shift, type) \

	aarch64_insn_gen_movewide(Rd, imm16, shift, \

arch/arm64/net/bpf_jit_comp.c

+20 −2
Original line number Diff line number Diff line
@@ -289,23 +289,41 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) 
	case BPF_ALU | BPF_END | BPF_FROM_BE:

#ifdef CONFIG_CPU_BIG_ENDIAN

		if (BPF_SRC(code) == BPF_FROM_BE)

			break;

			goto emit_bswap_uxt;

#else /* !CONFIG_CPU_BIG_ENDIAN */

		if (BPF_SRC(code) == BPF_FROM_LE)

			break;

			goto emit_bswap_uxt;

#endif

		switch (imm) {

		case 16:

			emit(A64_REV16(is64, dst, dst), ctx);

			/* zero-extend 16 bits into 64 bits */

			emit(A64_UXTH(is64, dst, dst), ctx);

			break;

		case 32:

			emit(A64_REV32(is64, dst, dst), ctx);

			/* upper 32 bits already cleared */

			break;

		case 64:

			emit(A64_REV64(dst, dst), ctx);

			break;

		}

		break;

emit_bswap_uxt:

		switch (imm) {

		case 16:

			/* zero-extend 16 bits into 64 bits */

			emit(A64_UXTH(is64, dst, dst), ctx);

			break;

		case 32:

			/* zero-extend 32 bits into 64 bits */

			emit(A64_UXTW(is64, dst, dst), ctx);

			break;

		case 64:

			/* nop */

			break;

		}

		break;

	/* dst = imm */

	case BPF_ALU | BPF_MOV | BPF_K:

	case BPF_ALU64 | BPF_MOV | BPF_K: