Currently, user array duplications are sometimes done without an
overflow check. Sometimes the checks are done manually; sometimes the
array size is calculated with array_size() and sometimes by calculating
n * size directly in code.
Introduce wrappers for arrays for memdup_user() and vmemdup_user() to
provide a standardized and safe way for duplicating user arrays.
This is both for new code as well as replacing usage of (v)memdup_user()
in existing code that uses, e.g., n * size to calculate array sizes.
Suggested-by: David Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Philipp Stanner <pstanner@xxxxxxxxxx>
---
include/linux/string.h | 42 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/include/linux/string.h b/include/linux/string.h
index dbfc66400050..0e8e7a40bae7 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -6,6 +6,8 @@
#include <linux/types.h> /* for size_t */
#include <linux/stddef.h> /* for NULL */
#include <linux/errno.h> /* for E2BIG */
+#include <linux/overflow.h> /* for check_mul_overflow() */
+#include <linux/err.h> /* for ERR_PTR() */
#include <linux/stdarg.h>
#include <uapi/linux/string.h>
@@ -14,6 +16,46 @@ extern void *memdup_user(const void __user *, size_t);
extern void *vmemdup_user(const void __user *, size_t);
extern void *memdup_user_nul(const void __user *, size_t);
+/**
+ * memdup_array_user - duplicate array from user space
+ *
+ * @src: source address in user space
+ * @n: number of array members to copy
+ * @size: size of one array member
+ *
+ * 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)
+{
+ size_t nbytes;
+
+ if (unlikely(check_mul_overflow(n, size, &nbytes)))
+ return ERR_PTR(-EINVAL);
+
+ return memdup_user(src, nbytes);
+}
+
+/**
+ * vmemdup_array_user - duplicate array from user space
+ *
+ * @src: source address in user space
+ * @n: number of array members to copy
+ * @size: size of one array member
+ *
+ * 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)
+{
+ size_t nbytes;
+
+ if (unlikely(check_mul_overflow(n, size, &nbytes)))
+ return ERR_PTR(-EINVAL);
+
+ return vmemdup_user(src, nbytes);
+}
+
/*
* Include machine specific inline routines
*/
--
2.41.0
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