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Commit 610a77e0 authored by Li Zefan's avatar Li Zefan Committed by Linus Torvalds
Browse files

memdup_user(): introduce 



I notice there are many places doing copy_from_user() which follows
kmalloc():

        dst = kmalloc(len, GFP_KERNEL);
        if (!dst)
                return -ENOMEM;
        if (copy_from_user(dst, src, len)) {
		kfree(dst);
		return -EFAULT
	}

memdup_user() is a wrapper of the above code.  With this new function, we
don't have to write 'len' twice, which can lead to typos/mistakes.  It
also produces smaller code and kernel text.

A quick grep shows 250+ places where memdup_user() *may* be used.  I'll
prepare a patchset to do this conversion.

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Americo Wang <xiyou.wangcong@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e2f17d94

include/linux/string.h

+1 −0
Original line number Diff line number Diff line
@@ -12,6 +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);



/*

 * Include machine specific inline routines

mm/util.c

+30 −0
Original line number Diff line number Diff line
@@ -69,6 +69,36 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp) 
}

EXPORT_SYMBOL(kmemdup);



/**

 * memdup_user - duplicate memory region from user space

 *

 * @src: source address in user space

 * @len: number of bytes to copy

 *

 * Returns an ERR_PTR() on failure.

 */

void *memdup_user(const void __user *src, size_t len)

{

	void *p;



	/*

	 * 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);



	if (copy_from_user(p, src, len)) {

		kfree(p);

		return ERR_PTR(-EFAULT);

	}



	return p;

}

EXPORT_SYMBOL(memdup_user);



/**

 * __krealloc - like krealloc() but don't free @p.

 * @p: object to reallocate memory for.