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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>
This commit is contained in:
Markus Kötter 2011-12-17 11:39:08 +00:00 committed by David S. Miller
parent d1388dacbb
commit a03ffcf873
1 changed files with 2 additions and 2 deletions
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4
arch/x86/net/bpf_jit_comp.c
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@ -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);