1 files changed, 172 insertions, 0 deletions
diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
new file mode 100644
index 000000000000..3e6c8e9d67ae
--- /dev/null
+++ b/include/linux/sockptr.h
@@ -0,0 +1,172 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2020 Christoph Hellwig.
+ *
+ * Support for "universal" pointers that can point to either kernel or userspace
+ * memory.
+ */
+#ifndef _LINUX_SOCKPTR_H
+#define _LINUX_SOCKPTR_H
+
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+typedef struct {
+	union {
+		void		*kernel;
+		void __user	*user;
+	};
+	bool		is_kernel : 1;
+} sockptr_t;
+
+static inline bool sockptr_is_kernel(sockptr_t sockptr)
+{
+	return sockptr.is_kernel;
+}
+
+static inline sockptr_t KERNEL_SOCKPTR(void *p)
+{
+	return (sockptr_t) { .kernel = p, .is_kernel = true };
+}
+
+static inline sockptr_t USER_SOCKPTR(void __user *p)
+{
+	return (sockptr_t) { .user = p };
+}
+
+static inline bool sockptr_is_null(sockptr_t sockptr)
+{
+	if (sockptr_is_kernel(sockptr))
+		return !sockptr.kernel;
+	return !sockptr.user;
+}
+
+static inline int copy_from_sockptr_offset(void *dst, sockptr_t src,
+		size_t offset, size_t size)
+{
+	if (!sockptr_is_kernel(src))
+		return copy_from_user(dst, src.user + offset, size);
+	memcpy(dst, src.kernel + offset, size);
+	return 0;
+}
+
+/* Deprecated.
+ * This is unsafe, unless caller checked user provided optlen.
+ * Prefer copy_safe_from_sockptr() instead.
+ *
+ * Returns 0 for success, or number of bytes not copied on error.
+ */
+static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
+{
+	return copy_from_sockptr_offset(dst, src, 0, size);
+}
+
+/**
+ * copy_safe_from_sockptr: copy a struct from sockptr
+ * @dst:   Destination address, in kernel space. This buffer must be @ksize
+ *         bytes long.
+ * @ksize: Size of @dst struct.
+ * @optval: Source address. (in user or kernel space)
+ * @optlen: Size of @optval data.
+ *
+ * Returns:
+ *  * -EINVAL: @optlen < @ksize
+ *  * -EFAULT: access to userspace failed.
+ *  * 0 : @ksize bytes were copied
+ */
+static inline int copy_safe_from_sockptr(void *dst, size_t ksize,
+					 sockptr_t optval, unsigned int optlen)
+{
+	if (optlen < ksize)
+		return -EINVAL;
+	if (copy_from_sockptr(dst, optval, ksize))
+		return -EFAULT;
+	return 0;
+}
+
+static inline int copy_struct_from_sockptr(void *dst, size_t ksize,
+		sockptr_t src, size_t usize)
+{
+	size_t size = min(ksize, usize);
+	size_t rest = max(ksize, usize) - size;
+
+	if (!sockptr_is_kernel(src))
+		return copy_struct_from_user(dst, ksize, src.user, size);
+
+	if (usize < ksize) {
+		memset(dst + size, 0, rest);
+	} else if (usize > ksize) {
+		char *p = src.kernel;
+
+		while (rest--) {
+			if (*p++)
+				return -E2BIG;
+		}
+	}
+	memcpy(dst, src.kernel, size);
+	return 0;
+}
+
+static inline int copy_to_sockptr_offset(sockptr_t dst, size_t offset,
+		const void *src, size_t size)
+{
+	if (!sockptr_is_kernel(dst))
+		return copy_to_user(dst.user + offset, src, size);
+	memcpy(dst.kernel + offset, src, size);
+	return 0;
+}
+
+static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
+{
+	return copy_to_sockptr_offset(dst, 0, src, size);
+}
+
+static inline void *memdup_sockptr_noprof(sockptr_t src, size_t len)
+{
+	void *p = kmalloc_track_caller_noprof(len, GFP_USER | __GFP_NOWARN);
+
+	if (!p)
+		return ERR_PTR(-ENOMEM);
+	if (copy_from_sockptr(p, src, len)) {
+		kfree(p);
+		return ERR_PTR(-EFAULT);
+	}
+	return p;
+}
+#define memdup_sockptr(...)	alloc_hooks(memdup_sockptr_noprof(__VA_ARGS__))
+
+static inline void *memdup_sockptr_nul_noprof(sockptr_t src, size_t len)
+{
+	char *p = kmalloc_track_caller_noprof(len + 1, GFP_KERNEL);
+
+	if (!p)
+		return ERR_PTR(-ENOMEM);
+	if (copy_from_sockptr(p, src, len)) {
+		kfree(p);
+		return ERR_PTR(-EFAULT);
+	}
+	p[len] = '\0';
+	return p;
+}
+#define memdup_sockptr_nul(...)	alloc_hooks(memdup_sockptr_nul_noprof(__VA_ARGS__))
+
+static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
+{
+	if (sockptr_is_kernel(src)) {
+		size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
+
+		memcpy(dst, src.kernel, len);
+		return len;
+	}
+	return strncpy_from_user(dst, src.user, count);
+}
+
+static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
+				       size_t size)
+{
+	if (!sockptr_is_kernel(src))
+		return check_zeroed_user(src.user + offset, size);
+	return memchr_inv(src.kernel + offset, 0, size) == NULL;
+}
+
+#endif /* _LINUX_SOCKPTR_H */