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>

diff --git a/include/linux/string.h b/include/linux/string.h
index 86aa6cd351675c2349a2ef37b95f35ab6757bf1d..10e5177bb49c05329bda70d5b1b94330837e16f7 100644 (file)
--- 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);

diff --git a/lib/fortify_kunit.c b/lib/fortify_kunit.c
index 306522fd0aa2f1b74674b3b7f7718baeac874516..d2377e00caab43883a5e1516d029cc28109c1872 100644 (file)
--- a/lib/fortify_kunit.c
+++ b/lib/fortify_kunit.c
@@ -363,6 +363,31 @@ DEFINE_ALLOC_SIZE_TEST_PAIR(kvmalloc)
 } while (0)
 DEFINE_ALLOC_SIZE_TEST_PAIR(devm_kmalloc)
 
+static const char * const test_strs[] = {
+       "",
+       "Hello there",
+       "A longer string, just for variety",
+};
+
+#define TEST_realloc(checker)  do {                                    \
+       gfp_t gfp = GFP_KERNEL;                                         \
+       size_t len;                                                     \
+       int i;                                                          \
+                                                                       \
+       for (i = 0; i < ARRAY_SIZE(test_strs); i++) {                   \
+               len = strlen(test_strs[i]);                             \
+               KUNIT_EXPECT_EQ(test, __builtin_constant_p(len), 0);    \
+               checker(len, kmemdup_array(test_strs[i], len, 1, gfp),  \
+                       kfree(p));                                      \
+               checker(len, kmemdup(test_strs[i], len, gfp),           \
+                       kfree(p));                                      \
+       }                                                               \
+} while (0)
+static void fortify_test_realloc_size(struct kunit *test)
+{
+       TEST_realloc(check_dynamic);
+}
+
 /*
  * We can't have an array at the end of a structure or else
  * builds without -fstrict-flex-arrays=3 will report them as
@@ -1046,6 +1071,7 @@ static struct kunit_case fortify_test_cases[] = {
        KUNIT_CASE(fortify_test_alloc_size_kvmalloc_dynamic),
        KUNIT_CASE(fortify_test_alloc_size_devm_kmalloc_const),
        KUNIT_CASE(fortify_test_alloc_size_devm_kmalloc_dynamic),
+       KUNIT_CASE(fortify_test_realloc_size),
        KUNIT_CASE(fortify_test_strlen),
        KUNIT_CASE(fortify_test_strnlen),
        KUNIT_CASE(fortify_test_strcpy),