string: Add additional __realloc_size() annotations for "dup" helpers

Several other "dup"-style interfaces could use the __realloc_size()
attribute. (As a reminder to myself and others: "realloc" is used here
instead of "alloc" because the "alloc_size" attribute implies that the
memory contents are uninitialized. Since we're copying contents into the
resulting allocation, it must use "realloc_size" to avoid confusing the
compiler's optimization passes.)

Add KUnit test coverage where possible. (KUnit still does not have the
ability to manipulate userspace memory.)

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://lore.kernel.org/r/20240502145218.it.729-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 8 insertions, 5 deletions

diff --git a/include/linux/string.h b/include/linux/string.h
index 86aa6cd35167..10e5177bb49c 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -14,8 +14,8 @@
 #include <uapi/linux/string.h>
 
 extern char *strndup_user(const char __user *, long);
-extern void *memdup_user(const void __user *, size_t);
-extern void *vmemdup_user(const void __user *, size_t);
+extern void *memdup_user(const void __user *, size_t) __realloc_size(2);
+extern void *vmemdup_user(const void __user *, size_t) __realloc_size(2);
 extern void *memdup_user_nul(const void __user *, size_t);
 
 /**
@@ -27,7 +27,8 @@ extern void *memdup_user_nul(const void __user *, size_t);
  * Return: an ERR_PTR() on failure. Result is physically
  * contiguous, to be freed by kfree().
  */
-static inline void *memdup_array_user(const void __user *src, size_t n, size_t size)
+static inline __realloc_size(2, 3)
+void *memdup_array_user(const void __user *src, size_t n, size_t size)
 {
 	size_t nbytes;
 
@@ -46,7 +47,8 @@ static inline void *memdup_array_user(const void __user *src, size_t n, size_t s
  * Return: an ERR_PTR() on failure. Result may be not
  * physically contiguous. Use kvfree() to free.
  */
-static inline void *vmemdup_array_user(const void __user *src, size_t n, size_t size)
+static inline __realloc_size(2, 3)
+void *vmemdup_array_user(const void __user *src, size_t n, size_t size)
 {
 	size_t nbytes;
 
@@ -285,7 +287,8 @@ extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
 extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 extern void *kvmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 extern char *kmemdup_nul(const char *s, size_t len, gfp_t gfp);
-extern void *kmemdup_array(const void *src, size_t element_size, size_t count, gfp_t gfp);
+extern void *kmemdup_array(const void *src, size_t element_size, size_t count, gfp_t gfp)
+		__realloc_size(2, 3);
 
 /* lib/argv_split.c */
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);