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authorDianzhang Chen <dianzhangchen0@gmail.com>2019-06-25 23:30:17 +0800
committerThomas Gleixner <tglx@linutronix.de>2019-06-27 23:48:04 +0200
commit31a2fbb390fee4231281b939e1979e810f945415 (patch)
parentab3765a050f7bea942f114d07278e1775e38199b (diff)
x86/ptrace: Fix possible spectre-v1 in ptrace_get_debugreg()
The index to access the threads ptrace_bps is controlled by userspace via syscall: sys_ptrace(), hence leading to a potential exploitation of the Spectre variant 1 vulnerability. The index can be controlled from: ptrace -> arch_ptrace -> ptrace_get_debugreg. Fix this by sanitizing the user supplied index before using it access thread->ptrace_bps. Signed-off-by: Dianzhang Chen <dianzhangchen0@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: bp@alien8.de Cc: hpa@zytor.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1561476617-3759-1-git-send-email-dianzhangchen0@gmail.com
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index a166c960bc9e..cbac64659dc4 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -25,6 +25,7 @@
#include <linux/rcupdate.h>
#include <linux/export.h>
#include <linux/context_tracking.h>
+#include <linux/nospec.h>
#include <linux/uaccess.h>
#include <asm/pgtable.h>
@@ -643,9 +644,11 @@ static unsigned long ptrace_get_debugreg(struct task_struct *tsk, int n)
struct thread_struct *thread = &tsk->thread;
unsigned long val = 0;
+ int index = n;
if (n < HBP_NUM) {
- struct perf_event *bp = thread->ptrace_bps[n];
+ index = array_index_nospec(index, HBP_NUM);
+ struct perf_event *bp = thread->ptrace_bps[index];
if (bp)
val = bp->hw.info.address;