From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@zeniv.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH 01/11] uptr: add a new "universal pointer" type
Date: Wed, 24 Jun 2020 18:28:51 +0200 [thread overview]
Message-ID: <20200624162901.1814136-2-hch@lst.de> (raw)
In-Reply-To: <20200624162901.1814136-1-hch@lst.de>
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. For
architectures like x86 that have non-overlapping user and kernel
address space it just is a union and uses a TASK_SIZE check to
select the proper copy routine. For architectures with overlapping
address spaces a flag to indicate the address space is used instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
include/linux/uptr.h | 72 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 72 insertions(+)
create mode 100644 include/linux/uptr.h
diff --git a/include/linux/uptr.h b/include/linux/uptr.h
new file mode 100644
index 00000000000000..1373511f9897b4
--- /dev/null
+++ b/include/linux/uptr.h
@@ -0,0 +1,72 @@
+/* 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_UPTR_H
+#define _LINUX_UPTR_H
+
+#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+typedef union {
+ void *kernel;
+ void __user *user;
+} uptr_t;
+
+static inline uptr_t USER_UPTR(void __user *p)
+{
+ return (uptr_t) { .user = p };
+}
+
+static inline uptr_t KERNEL_UPTR(void *p)
+{
+ return (uptr_t) { .kernel = p };
+}
+
+static inline bool uptr_is_kernel(uptr_t uptr)
+{
+ return (unsigned long)uptr.kernel >= TASK_SIZE;
+}
+#else /* CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE */
+typedef struct {
+ union {
+ void *kernel;
+ void __user *user;
+ };
+ bool is_kernel : 1;
+} uptr_t;
+
+static inline uptr_t USER_UPTR(void __user *p)
+{
+ return (uptr_t) { .user = p };
+}
+
+static inline uptr_t KERNEL_UPTR(void *p)
+{
+ return (uptr_t) { .kernel = p, .is_kernel = true };
+}
+
+static inline bool uptr_is_kernel(uptr_t uptr)
+{
+ return uptr.is_kernel;
+}
+#endif /* CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE */
+
+static inline int copy_from_uptr(void *dst, uptr_t src, size_t size)
+{
+ if (!uptr_is_kernel(src))
+ return copy_from_user(dst, src.user, size);
+ memcpy(dst, src.kernel, size);
+ return 0;
+}
+
+static inline int copy_to_uptr(uptr_t dst, const void *src, size_t size)
+{
+ if (!uptr_is_kernel(dst))
+ return copy_to_user(dst.user, src, size);
+ memcpy(dst.kernel, src, size);
+ return 0;
+}
+
+#endif /* _LINUX_UPTR_H */
--
2.26.2
next prev parent reply other threads:[~2020-06-24 16:29 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 16:28 [RFC] stop using ->read and ->write for kernel access Christoph Hellwig
2020-06-24 16:28 ` Christoph Hellwig [this message]
2020-06-24 16:28 ` [PATCH 02/11] fs: factor out a set_fmode_can_read_write helper Christoph Hellwig
2020-06-24 16:28 ` [PATCH 03/11] fs: add new read_uptr and write_uptr file operations Christoph Hellwig
2020-06-24 17:19 ` Linus Torvalds
2020-06-24 17:55 ` Christoph Hellwig
2020-06-24 18:11 ` Linus Torvalds
2020-06-24 18:14 ` Christoph Hellwig
2020-06-24 18:20 ` Linus Torvalds
2020-06-24 18:24 ` Christoph Hellwig
2020-06-24 18:29 ` Matthew Wilcox
2020-06-24 18:31 ` Christoph Hellwig
2020-06-24 18:15 ` Linus Torvalds
2020-06-27 10:49 ` David Laight
2020-06-27 16:33 ` Linus Torvalds
2020-06-29 8:21 ` David Laight
2020-06-29 15:29 ` Christoph Hellwig
2020-06-29 17:02 ` Linus Torvalds
2020-06-29 18:07 ` Christoph Hellwig
2020-06-29 18:29 ` Linus Torvalds
2020-06-29 18:36 ` Christoph Hellwig
2020-06-29 19:10 ` Linus Torvalds
2020-06-30 7:04 ` Christoph Hellwig
2020-06-30 7:51 ` David Laight
2020-07-08 5:14 ` Luis Chamberlain
2020-06-24 17:56 ` Matthew Wilcox
2020-06-24 17:59 ` Christoph Hellwig
2020-06-24 18:37 ` Christoph Hellwig
2020-06-24 18:43 ` Matthew Wilcox
2020-06-24 16:28 ` [PATCH 04/11] sysctl: switch to ->{read,write}_uptr Christoph Hellwig
2020-06-24 16:28 ` [PATCH 05/11] fs: refactor new_sync_read Christoph Hellwig
2020-06-24 16:28 ` [PATCH 06/11] proc: add a read_iter method to proc proc_ops Christoph Hellwig
2020-06-24 16:28 ` [PATCH 07/11] seq_file: add seq_read_iter Christoph Hellwig
2020-06-24 16:28 ` [PATCH 08/11] seq_file: switch over direct seq_read method calls to seq_read_iter Christoph Hellwig
2020-06-24 16:28 ` [PATCH 09/11] proc: " Christoph Hellwig
2020-06-24 16:29 ` [PATCH 10/11] fs: don't allow kernel reads and writes using ->read and ->write Christoph Hellwig
2020-06-24 16:29 ` [PATCH 11/11] fs: don't allow splice read/write without explicit ops Christoph Hellwig
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