From 20aa7b21b1cbd1aa3fbf5fc14da5f7484a61a824 Mon Sep 17 00:00:00 2001
From: Andrew Morton <akpm@osdl.org>
Date: Wed, 6 Dec 2006 20:36:40 -0800
Subject: [PATCH] [PATCH] probe_kernel_address() needs to do set_fs()
probe_kernel_address() purports to be generic, only it forgot to select
KERNEL_DS, so it presently won't work right on all architectures.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
include/linux/uaccess.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 67918c22339c5..76c3fe325101c 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -65,14 +65,22 @@ static inline unsigned long __copy_from_user_nocache(void *to,
* do_page_fault() doesn't attempt to take mmap_sem. This makes
* probe_kernel_address() suitable for use within regions where the caller
* already holds mmap_sem, or other locks which nest inside mmap_sem.
+ * This must be a macro because __get_user() needs to know the types of the
+ * args.
+ *
+ * We don't include enough header files to be able to do the set_fs(). We
+ * require that the probe_kernel_address() caller will do that.
*/
#define probe_kernel_address(addr, retval) \
({ \
long ret; \
+ mm_segment_t old_fs = get_fs(); \
\
+ set_fs(KERNEL_DS); \
pagefault_disable(); \
ret = __get_user(retval, addr); \
pagefault_enable(); \
+ set_fs(old_fs); \
ret; \
})
--
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