Patch "string.h: add array-wrappers for (v)memdup_user()" has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    string.h: add array-wrappers for (v)memdup_user()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     string.h-add-array-wrappers-for-v-memdup_user.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit e1a1b2295ab6d3c2d7874b64ba48f4cefd279822
Author: Philipp Stanner <pstanner@xxxxxxxxxx>
Date:   Wed Sep 20 14:36:09 2023 +0200

    string.h: add array-wrappers for (v)memdup_user()
    
    [ Upstream commit 313ebe47d75558511aa1237b6e35c663b5c0ec6f ]
    
    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>
    Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
    Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Reviewed-by: Zack Rusin <zackr@xxxxxxxxxx>
    Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
    Link: https://patchwork.freedesktop.org/patch/msgid/20230920123612.16914-3-pstanner@xxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/string.h b/include/linux/string.h
index d68097b4f600b..3b9f5abe5ee83 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -5,7 +5,9 @@
 #include <linux/compiler.h>	/* for inline */
 #include <linux/types.h>	/* for size_t */
 #include <linux/stddef.h>	/* for NULL */
+#include <linux/err.h>		/* for ERR_PTR() */
 #include <linux/errno.h>	/* for E2BIG */
+#include <linux/overflow.h>	/* for check_mul_overflow() */
 #include <linux/stdarg.h>
 #include <uapi/linux/string.h>
 
@@ -14,6 +16,44 @@ 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 (check_mul_overflow(n, size, &nbytes))
+		return ERR_PTR(-EOVERFLOW);
+
+	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 (check_mul_overflow(n, size, &nbytes))
+		return ERR_PTR(-EOVERFLOW);
+
+	return vmemdup_user(src, nbytes);
+}
+
 /*
  * Include machine specific inline routines
  */



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