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Message-ID: <93001a9f3f101be0f374080090f9c32df73ca773.1694202430.git.pstanner@redhat.com>
Date: Fri, 8 Sep 2023 21:59:40 +0200
From: Philipp Stanner <pstanner@...hat.com>
To: Kees Cook <keescook@...omium.org>,
Andy Shevchenko <andy@...nel.org>,
Eric Biederman <ebiederm@...ssion.com>,
Christian Brauner <brauner@...nel.org>,
David Disseldorp <ddiss@...e.de>,
Luis Chamberlain <mcgrof@...nel.org>,
Siddh Raman Pant <code@...dh.me>,
Nick Alcock <nick.alcock@...cle.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>, Zack Rusin <zackr@...are.com>
Cc: VMware Graphics Reviewers <linux-graphics-maintainer@...are.com>,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
kexec@...ts.infradead.org, linux-hardening@...r.kernel.org,
Philipp Stanner <pstanner@...hat.com>,
David Airlie <airlied@...hat.com>
Subject: [PATCH v2 1/5] string.h: add array-wrappers for (v)memdup_user()
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@...hat.com>
Signed-off-by: Philipp Stanner <pstanner@...hat.com>
---
include/linux/string.h | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/include/linux/string.h b/include/linux/string.h
index dbfc66400050..8c9fc76c7154 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 (unlikely(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 (unlikely(check_mul_overflow(n, size, &nbytes)))
+ return ERR_PTR(-EOVERFLOW);
+
+ return vmemdup_user(src, nbytes);
+}
+
/*
* Include machine specific inline routines
*/
--
2.41.0
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