Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 19fc99d0 authored by Nicolas Schichan's avatar Nicolas Schichan Committed by David S. Miller
Browse files

ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction. 



In that case, emit_udiv() will be called with rn == ARM_R0 (r_scratch)
and loading rm first into ARM_R0 will result in jit_udiv() function
being called the same dividend and divisor. Fix that by loading rn
first into ARM_R1 and then rm into ARM_R0.

Signed-off-by: default avatarNicolas Schichan <nschichan@freebox.fr>
Cc: <stable@vger.kernel.org> # v3.13+
Fixes: aee636c4 (bpf: do not use reciprocal divide)
Acked-by: default avatarMircea Gherzan <mgherzan@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 78f5b899

arch/arm/net/bpf_jit_32.c

+13 −2
Original line number Diff line number Diff line
@@ -449,10 +449,21 @@ static inline void emit_udiv(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx) 
		return;

	}

#endif

	if (rm != ARM_R0)

		emit(ARM_MOV_R(ARM_R0, rm), ctx);



	/*

	 * For BPF_ALU | BPF_DIV | BPF_K instructions, rm is ARM_R4

	 * (r_A) and rn is ARM_R0 (r_scratch) so load rn first into

	 * ARM_R1 to avoid accidentally overwriting ARM_R0 with rm

	 * before using it as a source for ARM_R1.

	 *

	 * For BPF_ALU | BPF_DIV | BPF_X rm is ARM_R4 (r_A) and rn is

	 * ARM_R5 (r_X) so there is no particular register overlap

	 * issues.

	 */

	if (rn != ARM_R1)

		emit(ARM_MOV_R(ARM_R1, rn), ctx);

	if (rm != ARM_R0)

		emit(ARM_MOV_R(ARM_R0, rm), ctx);



	ctx->seen |= SEEN_CALL;

	emit_mov_i(ARM_R3, (u32)jit_udiv, ctx);