memdup_user(): introduce (610a77e0) · Commits · 戴 / test

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:

Li 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:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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.

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