MIPS: bpf: Return error code if the offset is a negative number (55393ee5) · Commits · 戴 / test

Previously, the negative offset was not checked leading to failures due to trying to load data beyond the skb struct boundaries. Until we have proper asm helpers in place, it's best if we return ENOSUPP if K is negative when trying to JIT the filter or 0 during runtime if we do an indirect load where the value of X is unknown during build time. Signed-off-by:

Markos Chandras <markos.chandras@imgtec.com> Cc: David S. Miller <davem@davemloft.net> Cc: Daniel Borkmann <dborkman@redhat.com> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: netdev@vger.kernel.org Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/7123/ Signed-off-by:

Ralf Baechle <ralf@linux-mips.org>

arch/mips/net/bpf_jit.c

+23 −0

Original line number	Diff line number	Diff line
		@@ -331,6 +331,12 @@ static inline void emit_srl(unsigned int dst, unsigned int src,
		emit_instr(ctx, srl, dst, src, sa);
		}

		static inline void emit_slt(unsigned int dst, unsigned int src1,
		unsigned int src2, struct jit_ctx *ctx)
		{
		emit_instr(ctx, slt, dst, src1, src2);
		}

		static inline void emit_sltu(unsigned int dst, unsigned int src1,
		unsigned int src2, struct jit_ctx *ctx)
		{
		@@ -816,8 +822,21 @@ static int build_body(struct jit_ctx *ctx)
		/* A <- P[k:1] */
		load_order = 0;
		load:
		/* the interpreter will deal with the negative K */
		if ((int)k < 0)
		return -ENOTSUPP;

		emit_load_imm(r_off, k, ctx);
		load_common:
		/*
		* We may got here from the indirect loads so
		* return if offset is negative.
		*/
		emit_slt(r_s0, r_off, r_zero, ctx);
		emit_bcond(MIPS_COND_NE, r_s0, r_zero,
		b_imm(prog->len, ctx), ctx);
		emit_reg_move(r_ret, r_zero, ctx);

		ctx->flags \|= SEEN_CALL \| SEEN_OFF \| SEEN_S0 \|
		SEEN_SKB \| SEEN_A;

		@@ -880,6 +899,10 @@ load_ind:
		emit_load(r_X, r_skb, off, ctx);
		break;
		case BPF_LDX \| BPF_B \| BPF_MSH:
		/* the interpreter will deal with the negative K */
		if ((int)k < 0)
		return -ENOTSUPP;

		/* X <- 4 * (P[k:1] & 0xf) */
		ctx->flags \|= SEEN_X \| SEEN_CALL \| SEEN_S0 \| SEEN_SKB;
		/* Load offset to a1 */

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