Patch "ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction." has been added to the 4.0-stable tree

Patch "ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction." has been added to the 4.0-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

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

to the 4.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-net-fix-emit_udiv-for-bpf_alu-bpf_div-bpf_k-intruction.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 19fc99d0c6ba7d9b65456496b5bb2169d5f74cd0 Mon Sep 17 00:00:00 2001
From: Nicolas Schichan <nschichan@freebox.fr>
Date: Wed, 6 May 2015 18:31:56 +0200
Subject: ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction.

From: Nicolas Schichan <nschichan@freebox.fr>

commit 19fc99d0c6ba7d9b65456496b5bb2169d5f74cd0 upstream.

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: Nicolas Schichan <nschichan@freebox.fr>
Fixes: aee636c4809f (bpf: do not use reciprocal divide)
Acked-by: Mircea Gherzan <mgherzan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm/net/bpf_jit_32.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -449,10 +449,21 @@ static inline void emit_udiv(u8 rd, u8 r
 		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);


Patches currently in stable-queue which might be from nschichan@freebox.fr are

queue-4.0/arm-net-fix-emit_udiv-for-bpf_alu-bpf_div-bpf_k-intruction.patch