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Subject[PATCH 4.14 57/57] x86/ptrace: fix up botched merge of spectrev1 fix
Date
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

I incorrectly merged commit 31a2fbb390fe ("x86/ptrace: Fix possible
spectre-v1 in ptrace_get_debugreg()") when backporting it, as was
graciously pointed out at
https://grsecurity.net/teardown_of_a_failed_linux_lts_spectre_fix.php

Resolve the upstream difference with the stable kernel merge to properly
protect things.

Reported-by: Brad Spengler <spender@grsecurity.net>
Cc: Dianzhang Chen <dianzhangchen0@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <bp@alien8.de>
Cc: <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/ptrace.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -652,11 +652,10 @@ static unsigned long ptrace_get_debugreg
{
struct thread_struct *thread = &tsk->thread;
unsigned long val = 0;
- int index = n;

if (n < HBP_NUM) {
+ int index = array_index_nospec(n, HBP_NUM);
struct perf_event *bp = thread->ptrace_bps[index];
- index = array_index_nospec(index, HBP_NUM);

if (bp)
val = bp->hw.info.address;

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