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authorAlexey Dobriyan <adobriyan@gmail.com>2006-10-01 02:27:20 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-01 03:39:19 -0400
commit1a2f67b459bb7846d4a15924face63eb2683acc2 (patch)
tree4c010d4c4220c9523342fb0daac90a433f36b53e /mm
parent9442e691e4aec85eba43ac60a3e77c77fd2e73a4 (diff)
[PATCH] kmemdup: introduce
One of idiomatic ways to duplicate a region of memory is dst = kmalloc(len, GFP_KERNEL); if (!dst) return -ENOMEM; memcpy(dst, src, len); which is neat code except a programmer needs to write size twice. Which sometimes leads to mistakes. If len passed to kmalloc is smaller that len passed to memcpy, it's straight overwrite-beyond-end. If len passed to memcpy is smaller than len passed to kmalloc, it's either a) legit behaviour ;-), or b) cloned buffer will contain garbage in second half. Slight trolling of commit lists shows several duplications bugs done exactly because of diverged lenghts: Linux: [CRYPTO]: Fix memcpy/memset args. [PATCH] memcpy/memset fixes OpenBSD: kerberosV/src/lib/asn1: der_copy.c:1.4 If programmer is given only one place to play with lengths, I believe, such mistakes could be avoided. With kmemdup, the snippet above will be rewritten as: dst = kmemdup(src, len, GFP_KERNEL); if (!dst) return -ENOMEM; This also leads to smaller code (kzalloc effect). Quick grep shows 200+ places where kmemdup() can be used. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/util.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c
index 7368479220b3..e14fa84ef39a 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -40,6 +40,24 @@ char *kstrdup(const char *s, gfp_t gfp)
40} 40}
41EXPORT_SYMBOL(kstrdup); 41EXPORT_SYMBOL(kstrdup);
42 42
43/**
44 * kmemdup - duplicate region of memory
45 *
46 * @src: memory region to duplicate
47 * @len: memory region length
48 * @gfp: GFP mask to use
49 */
50void *kmemdup(const void *src, size_t len, gfp_t gfp)
51{
52 void *p;
53
54 p = ____kmalloc(len, gfp);
55 if (p)
56 memcpy(p, src, len);
57 return p;
58}
59EXPORT_SYMBOL(kmemdup);
60
43/* 61/*
44 * strndup_user - duplicate an existing string from user space 62 * strndup_user - duplicate an existing string from user space
45 * 63 *