[PATCH RFC v4 42/42] kmsan: x86/uprobes: unpoison regs in arch_uprobe_exception_notify()

[glider@google.com]

arch_uprobe_exception_notify() may receive register state without
valid KMSAN metadata, which will lead to false positives.
Explicitly unpoison args and args->regs to avoid this.

Signed-off-by: Alexander Potapenko <glider@google.com>
To: Alexander Potapenko <glider@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: linux-mm@kvack.org

---

This patch was split from "kmsan: disable instrumentation of certain
functions"

v4:
 - split this patch away

Change-Id: I466ef628b00362ab5eb1852c76baa8cdb06736d9
---
 arch/x86/kernel/uprobes.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 15e5aad8ac2c..bc156b016dc5 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -8,6 +8,7 @@
  *	Jim Keniston
  */
 #include <linux/kernel.h>
+#include <linux/kmsan-checks.h>
 #include <linux/sched.h>
 #include <linux/ptrace.h>
 #include <linux/uprobes.h>
@@ -997,9 +998,13 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
 {
 	struct die_args *args = data;
-	struct pt_regs *regs = args->regs;
+	struct pt_regs *regs;
 	int ret = NOTIFY_DONE;
 
+	kmsan_unpoison_shadow(args, sizeof(*args));
+	regs = args->regs;
+	if (regs)
+		kmsan_unpoison_shadow(regs, sizeof(*regs));
 	/* We are only interested in userspace traps */
 	if (regs && !user_mode(regs))
 		return NOTIFY_DONE;
-- 
2.24.1.735.g03f4e72817-goog