mm: kmsan: implement kmsan_memmove()

Provide a hook that can be used by custom memcpy implementations to tell
KMSAN that the metadata needs to be copied.  Without that, false positive
reports are possible in the cases where KMSAN fails to intercept memory
initialization.

Link: https://lore.kernel.org/all/3b7dbd88-0861-4638-b2d2-911c97a4cadf@I-love.SAKURA.ne.jp/
Link: https://lkml.kernel.org/r/20240320101851.2589698-1-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/kmsan-checks.h b/include/linux/kmsan-checks.h
index c4cae333deec5f24fb231b27c948560a4f0db69c..e1082dc40abc2ccd6b3ddab91c9f462b3f4725a1 100644 (file)
--- a/include/linux/kmsan-checks.h
+++ b/include/linux/kmsan-checks.h
@@ -61,6 +61,17 @@ void kmsan_check_memory(const void *address, size_t size);
 void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
                        size_t left);
 
+/**
+ * kmsan_memmove() - Notify KMSAN about a data copy within kernel.
+ * @to:   destination address in the kernel.
+ * @from: source address in the kernel.
+ * @size: number of bytes to copy.
+ *
+ * Invoked after non-instrumented version (e.g. implemented using assembly
+ * code) of memmove()/memcpy() is called, in order to copy KMSAN's metadata.
+ */
+void kmsan_memmove(void *to, const void *from, size_t to_copy);
+
 #else
 
 static inline void kmsan_poison_memory(const void *address, size_t size,
@@ -78,6 +89,10 @@ static inline void kmsan_copy_to_user(void __user *to, const void *from,
 {
 }
 
+static inline void kmsan_memmove(void *to, const void *from, size_t to_copy)
+{
+}
+
 #endif
 
 #endif /* _LINUX_KMSAN_CHECKS_H */

diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 0b09daa188ef6cd6ebcbe9ea587a59a8c1aa6aff..22e8657800effb35dcfe84d1c3a8f4c861c470b5 100644 (file)
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -285,6 +285,17 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
 }
 EXPORT_SYMBOL(kmsan_copy_to_user);
 
+void kmsan_memmove(void *to, const void *from, size_t size)
+{
+       if (!kmsan_enabled || kmsan_in_runtime())
+               return;
+
+       kmsan_enter_runtime();
+       kmsan_internal_memmove_metadata(to, (void *)from, size);
+       kmsan_leave_runtime();
+}
+EXPORT_SYMBOL(kmsan_memmove);
+
 /* Helper function to check an URB. */
 void kmsan_handle_urb(const struct urb *urb, bool is_out)
 {