1 files changed, 38 insertions, 0 deletions
diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 6f3e64b0b61f..5c0eb25d984d 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -205,6 +205,44 @@ void kmsan_iounmap_page_range(unsigned long start, unsigned long end)
 	kmsan_leave_runtime();
 }
 
+void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
+			size_t left)
+{
+	unsigned long ua_flags;
+
+	if (!kmsan_enabled || kmsan_in_runtime())
+		return;
+	/*
+	 * At this point we've copied the memory already. It's hard to check it
+	 * before copying, as the size of actually copied buffer is unknown.
+	 */
+
+	/* copy_to_user() may copy zero bytes. No need to check. */
+	if (!to_copy)
+		return;
+	/* Or maybe copy_to_user() failed to copy anything. */
+	if (to_copy <= left)
+		return;
+
+	ua_flags = user_access_save();
+	if ((u64)to < TASK_SIZE) {
+		/* This is a user memory access, check it. */
+		kmsan_internal_check_memory((void *)from, to_copy - left, to,
+					    REASON_COPY_TO_USER);
+	} else {
+		/* Otherwise this is a kernel memory access. This happens when a
+		 * compat syscall passes an argument allocated on the kernel
+		 * stack to a real syscall.
+		 * Don't check anything, just copy the shadow of the copied
+		 * bytes.
+		 */
+		kmsan_internal_memmove_metadata((void *)to, (void *)from,
+						to_copy - left);
+	}
+	user_access_restore(ua_flags);
+}
+EXPORT_SYMBOL(kmsan_copy_to_user);
+
 /* Functions from kmsan-checks.h follow. */
 void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)
 {