[v3,04/46] instrumented.h: allow instrumenting both sides of copy_from_user()

Commit Message

Alexander Potapenko April 26, 2022, 4:42 p.m. UTC

Introduce instrument_copy_from_user_before() and
instrument_copy_from_user_after() hooks to be invoked before and after
the call to copy_from_user().

KASAN and KCSAN will be only using instrument_copy_from_user_before(),
but for KMSAN we'll need to insert code after copy_from_user().

Signed-off-by: Alexander Potapenko <[e-mail]>
---
Link: https://linux-review.googlesource.com/id/I855034578f0b0f126734cbd734fb4ae1d3a6af99
---
 include/linux/instrumented.h | 21 +++++++++++++++++++--
 include/linux/uaccess.h      | 19 ++++++++++++++-----
 lib/iov_iter.c               |  9 ++++++---
 lib/usercopy.c               |  3 ++-
 4 files changed, 41 insertions(+), 11 deletions(-)

Patch

diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h
index 42faebbaa202a..ee8f7d17d34f5 100644
--- a/include/linux/instrumented.h
+++ b/include/linux/instrumented.h
@@ -120,7 +120,7 @@  instrument_copy_to_user(void __user *to, const void *from, unsigned long n)
 }
 
 /**
- * instrument_copy_from_user - instrument writes of copy_from_user
+ * instrument_copy_from_user_before - add instrumentation before copy_from_user
  *
  * Instrument writes to kernel memory, that are due to copy_from_user (and
  * variants). The instrumentation should be inserted before the accesses.
@@ -130,10 +130,27 @@  instrument_copy_to_user(void __user *to, const void *from, unsigned long n)
  * @n number of bytes to copy
  */
 static __always_inline void
-instrument_copy_from_user(const void *to, const void __user *from, unsigned long n)
+instrument_copy_from_user_before(const void *to, const void __user *from, unsigned long n)
 {
 	kasan_check_write(to, n);
 	kcsan_check_write(to, n);
 }
 
+/**
+ * instrument_copy_from_user_after - add instrumentation after copy_from_user
+ *
+ * Instrument writes to kernel memory, that are due to copy_from_user (and
+ * variants). The instrumentation should be inserted after the accesses.
+ *
+ * @to destination address
+ * @from source address
+ * @n number of bytes to copy
+ * @left number of bytes not copied (as returned by copy_from_user)
+ */
+static __always_inline void
+instrument_copy_from_user_after(const void *to, const void __user *from,
+				unsigned long n, unsigned long left)
+{
+}
+
 #endif /* _LINUX_INSTRUMENTED_H */
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 546179418ffa2..079bdea3b9dcd 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -58,20 +58,28 @@ 
 static __always_inline __must_check unsigned long
 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
 {
-	instrument_copy_from_user(to, from, n);
+	unsigned long res;
+
+	instrument_copy_from_user_before(to, from, n);
 	check_object_size(to, n, false);
-	return raw_copy_from_user(to, from, n);
+	res = raw_copy_from_user(to, from, n);
+	instrument_copy_from_user_after(to, from, n, res);
+	return res;
 }
 
 static __always_inline __must_check unsigned long
 __copy_from_user(void *to, const void __user *from, unsigned long n)
 {
+	unsigned long res;
+
 	might_fault();
+	instrument_copy_from_user_before(to, from, n);
 	if (should_fail_usercopy())
 		return n;
-	instrument_copy_from_user(to, from, n);
 	check_object_size(to, n, false);
-	return raw_copy_from_user(to, from, n);
+	res = raw_copy_from_user(to, from, n);
+	instrument_copy_from_user_after(to, from, n, res);
+	return res;
 }
 
 /**
@@ -115,8 +123,9 @@  _copy_from_user(void *to, const void __user *from, unsigned long n)
 	unsigned long res = n;
 	might_fault();
 	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
-		instrument_copy_from_user(to, from, n);
+		instrument_copy_from_user_before(to, from, n);
 		res = raw_copy_from_user(to, from, n);
+		instrument_copy_from_user_after(to, from, n, res);
 	}
 	if (unlikely(res))
 		memset(to + (n - res), 0, res);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 6dd5330f7a995..fb19401c29c4f 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -159,13 +159,16 @@  static int copyout(void __user *to, const void *from, size_t n)
 
 static int copyin(void *to, const void __user *from, size_t n)
 {
+	size_t res = n;
+
 	if (should_fail_usercopy())
 		return n;
 	if (access_ok(from, n)) {
-		instrument_copy_from_user(to, from, n);
-		n = raw_copy_from_user(to, from, n);
+		instrument_copy_from_user_before(to, from, n);
+		res = raw_copy_from_user(to, from, n);
+		instrument_copy_from_user_after(to, from, n, res);
 	}
-	return n;
+	return res;
 }
 
 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
diff --git a/lib/usercopy.c b/lib/usercopy.c
index 7413dd300516e..1505a52f23a01 100644
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -12,8 +12,9 @@  unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n
 	unsigned long res = n;
 	might_fault();
 	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
-		instrument_copy_from_user(to, from, n);
+		instrument_copy_from_user_before(to, from, n);
 		res = raw_copy_from_user(to, from, n);
+		instrument_copy_from_user_after(to, from, n, res);
 	}
 	if (unlikely(res))
 		memset(to + (n - res), 0, res);