From 610a77e04a8d9fe8764dc484e2182fa251ce1cc2 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Tue, 31 Mar 2009 15:23:16 -0700 Subject: [PATCH] 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: Li Zefan Cc: KOSAKI Motohiro Cc: Americo Wang Cc: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/string.h | 1 + mm/util.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/linux/string.h b/include/linux/string.h index d18fc198aa2..8852739f36d 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -12,6 +12,7 @@ #include /* for NULL */ extern char *strndup_user(const char __user *, long); +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 37eaccdf305..7c122e49f76 100644 --- a/mm/util.c +++ b/mm/util.c @@ -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. -- 2.41.1