patches/old/lib-stackdepot-kmsan-mark-api-outputs-as-initialized.patch

From: Alexander Potapenko <glider@google.com>
Subject: lib/stackdepot: kmsan: mark API outputs as initialized
Date: Mon, 6 Mar 2023 12:13:21 +0100

KMSAN does not instrument stackdepot and may treat memory allocated by it
as uninitialized.  This is not a problem for KMSAN itself, because its
functions calling stackdepot API are also not instrumented.  But other
kernel features (e.g.  netdev tracker) may access stack depot from
instrumented code, which will lead to false positives, unless we
explicitly mark stackdepot outputs as initialized.

Link: https://lkml.kernel.org/r/20230306111322.205724-1-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/stackdepot.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/lib/stackdepot.c~lib-stackdepot-kmsan-mark-api-outputs-as-initialized
+++ a/lib/stackdepot.c
@@ -17,6 +17,7 @@
 #include <linux/gfp.h>
 #include <linux/jhash.h>
 #include <linux/kernel.h>
+#include <linux/kmsan.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
 #include <linux/percpu.h>
@@ -306,6 +307,11 @@ depot_alloc_stack(unsigned long *entries
 	stack->handle.extra = 0;
 	memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
 	pool_offset += required_size;
+	/*
+	 * Let KMSAN know the stored stack record is initialized. This shall
+	 * prevent false positive reports if instrumented code accesses it.
+	 */
+	kmsan_unpoison_memory(stack, required_size);
 
 	return stack;
 }
@@ -465,6 +471,12 @@ unsigned int stack_depot_fetch(depot_sta
 	struct stack_record *stack;
 
 	*entries = NULL;
+	/*
+	 * Let KMSAN know *entries is initialized. This shall prevent false
+	 * positive reports if instrumented code accesses it.
+	 */
+	kmsan_unpoison_memory(entries, sizeof(*entries));
+
 	if (!handle)
 		return 0;
 
_