[3.19.y-ckt stable] Patch "x86: bpf_jit: fix FROM_BE16 and FROM_LE16/32 instructions" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    x86: bpf_jit: fix FROM_BE16 and FROM_LE16/32 instructions

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6bcaf66797cb2cb4c8b6c4a4f346b346164baab1 Mon Sep 17 00:00:00 2001
From: Alexei Starovoitov <ast at plumgrid.com>
Date: Mon, 11 May 2015 23:25:16 -0700
Subject: x86: bpf_jit: fix FROM_BE16 and FROM_LE16/32 instructions

commit 343f845b375989f1753f605902931fa939aa2223 upstream.

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: 89aa075832b0 ("net: sock: allow eBPF programs to be attached to sockets")
Signed-off-by: Alexei Starovoitov <ast at plumgrid.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/net/bpf_jit_comp.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 9875143..99f7610 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -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 */
--
1.9.1