The patch titled
Subject: lib/stackdepot: kmsan: mark API outputs as initialized
has been added to the -mm mm-unstable branch. Its filename is
lib-stackdepot-kmsan-mark-api-outputs-as-initialized.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-stackdepot-kmsan-mark-api-outputs-as-initialized.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
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@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- 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;
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
x86-kmsan-dont-rename-memintrinsics-in-uninstrumented-files.patch
kmsan-another-take-at-fixing-memcpy-tests.patch
x86-kmsan-use-c-versions-of-memset16-memset32-memset64.patch
kmsan-add-memsetxx-tests.patch
lib-stackdepot-kmsan-mark-api-outputs-as-initialized.patch
kmsan-add-test_stackdepot_roundtrip.patch
