From: Christoph Hellwig <hch@lst.de>
To: dccp@vger.kernel.org
Subject: [PATCH 04/26] net: add a new sockptr_t type
Date: Thu, 23 Jul 2020 06:08:46 +0000 [thread overview]
Message-ID: <20200723060908.50081-5-hch@lst.de> (raw)
Add a uptr_t type that can hold a pointer to either a user or kernel
memory region, and simply helpers to copy to and from it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
include/linux/sockptr.h | 104 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 104 insertions(+)
create mode 100644 include/linux/sockptr.h
diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
new file mode 100644
index 00000000000000..700856e13ea0c4
--- /dev/null
+++ b/include/linux/sockptr.h
@@ -0,0 +1,104 @@
+/* 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)
+{
+ return !sockptr.user && !sockptr.kernel;
+}
+
+static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
+{
+ if (!sockptr_is_kernel(src))
+ return copy_from_user(dst, src.user, size);
+ memcpy(dst, src.kernel, size);
+ return 0;
+}
+
+static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
+{
+ if (!sockptr_is_kernel(dst))
+ return copy_to_user(dst.user, src, size);
+ memcpy(dst.kernel, src, size);
+ return 0;
+}
+
+static inline void *memdup_sockptr(sockptr_t src, size_t len)
+{
+ void *p = kmalloc_track_caller(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;
+}
+
+static inline void *memdup_sockptr_nul(sockptr_t src, size_t len)
+{
+ char *p = kmalloc_track_caller(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;
+}
+
+static inline void sockptr_advance(sockptr_t sockptr, size_t len)
+{
+ if (sockptr_is_kernel(sockptr))
+ sockptr.kernel += len;
+ else
+ sockptr.user += len;
+}
+
+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);
+}
+
+#endif /* _LINUX_SOCKPTR_H */
--
2.27.0
next reply other threads:[~2020-07-23 6:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 6:08 Christoph Hellwig [this message]
2020-07-23 15:40 ` [PATCH 04/26] net: add a new sockptr_t type Jan Engelhardt
2020-07-23 16:40 ` Eric Dumazet
2020-07-23 16:44 ` Christoph Hellwig
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