From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Cc: Dianzhang Chen <dianzhangchen0@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: <bp@xxxxxxxxx>
Cc: <hpa@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -698,11 +698,10 @@ 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;
