linux-kernel - [PATCH] memdup_user: introduce, fix

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Date:	Tue, 10 Mar 2009 09:47:11 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Americo Wang <xiyou.wangcong@...il.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Roland Dreier <rdreier@...co.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: [PATCH] memdup_user: introduce, fix

Always use GFP_KERNEL in kmalloc(), since copy_from_user() can sleep and
cause pagefault, thus it's pointless to use GFP_NOFS or GFP_ATOMIC here.

Signed-off-by: Li Zefan <lizf@...fujitsu.com>
---

Against memdup_user-introduce.patch

---
 include/linux/string.h |    2 +-
 mm/util.c              |   10 +++++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index 79f30f3..0863885 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -12,7 +12,7 @@
 #include <linux/stddef.h>	/* for NULL */
 
 extern char *strndup_user(const char __user *, long);
-extern void *memdup_user(const void __user *, size_t, gfp_t);
+extern void *memdup_user(const void __user *, size_t);
 
 /*
  * Include machine specific inline routines
diff --git a/mm/util.c b/mm/util.c
index 3d21c21..7c122e4 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -74,15 +74,19 @@ EXPORT_SYMBOL(kmemdup);
  *
  * @src: source address in user space
  * @len: number of bytes to copy
- * @gfp: GFP mask to use
  *
  * Returns an ERR_PTR() on failure.
  */
-void *memdup_user(const void __user *src, size_t len, gfp_t gfp)
+void *memdup_user(const void __user *src, size_t len)
 {
 	void *p;
 
-	p = kmalloc_track_caller(len, gfp);
+	/*
+	 * Always use GFP_KERNEL, since copy_from_user() can sleep and
+	 * cause pagefault, which makes it pointless to use GFP_NOFS
+	 * or GFP_ATOMIC.
+	 */
+	p = kmalloc_track_caller(len, GFP_KERNEL);
 	if (!p)
 		return ERR_PTR(-ENOMEM);
 
-- 
1.5.4.rc3
--
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