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x86/ptrace: fix up botched merge of spectrev1 fix

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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>
This commit is contained in:
Greg Kroah-Hartman 2019-09-04 12:27:18 +02:00
parent 8c0932cd81
commit 61263fbe57
1 changed files with 1 additions and 2 deletions
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3
arch/x86/kernel/ptrace.c
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@ -698,11 +698,10 @@ static unsigned long ptrace_get_debugreg(struct task_struct *tsk, int n)
{ {
struct thread_struct *thread = &tsk->thread; struct thread_struct *thread = &tsk->thread;
unsigned long val = 0; unsigned long val = 0;
int index = n;
if (n < HBP_NUM) { if (n < HBP_NUM) {
int index = array_index_nospec(n, HBP_NUM);
struct perf_event *bp = thread->ptrace_bps[index]; struct perf_event *bp = thread->ptrace_bps[index];
index = array_index_nospec(index, HBP_NUM);
if (bp) if (bp)
val = bp->hw.info.address; val = bp->hw.info.address;