From a03ffcf873fe0f2565386ca8ef832144c42e67fa Mon Sep 17 00:00:00 2001
From: =?utf8?q?Markus=20K=C3=B6tter?= <nepenthesdev@gmail.com>
Date: Sat, 17 Dec 2011 11:39:08 +0000
Subject: [PATCH] net: bpf_jit: fix an off-one bug in x86_64 cond jump target
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x86 jump instruction size is 2 or 5 bytes (near/long jump), not 2 or 6
bytes.
In case a conditional jump is followed by a long jump, conditional jump
target is one byte past the start of target instruction.
Signed-off-by: Markus Kötter <nepenthesdev@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
arch/x86/net/bpf_jit_comp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index bfab3fa10edc..7b65f752c5f8 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -568,8 +568,8 @@ cond_branch: f_offset = addrs[i + filter[i].jf] - addrs[i];
break;
}
if (filter[i].jt != 0) {
- if (filter[i].jf)
- t_offset += is_near(f_offset) ? 2 : 6;
+ if (filter[i].jf && f_offset)
+ t_offset += is_near(f_offset) ? 2 : 5;
EMIT_COND_JMP(t_op, t_offset);
if (filter[i].jf)
EMIT_JMP(f_offset);
--
2.20.1