1a2f67b459
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>
94 lines
1.7 KiB
C
94 lines
1.7 KiB
C
#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/module.h>
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#include <linux/err.h>
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#include <asm/uaccess.h>
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/**
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* __kzalloc - allocate memory. The memory is set to zero.
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* @size: how many bytes of memory are required.
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* @flags: the type of memory to allocate.
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*/
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void *__kzalloc(size_t size, gfp_t flags)
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{
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void *ret = ____kmalloc(size, flags);
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if (ret)
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memset(ret, 0, size);
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return ret;
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}
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EXPORT_SYMBOL(__kzalloc);
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/*
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* kstrdup - allocate space for and copy an existing string
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*
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* @s: the string to duplicate
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* @gfp: the GFP mask used in the kmalloc() call when allocating memory
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*/
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char *kstrdup(const char *s, gfp_t gfp)
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{
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size_t len;
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char *buf;
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if (!s)
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return NULL;
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len = strlen(s) + 1;
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buf = ____kmalloc(len, gfp);
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if (buf)
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memcpy(buf, s, len);
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return buf;
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}
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EXPORT_SYMBOL(kstrdup);
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/**
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* kmemdup - duplicate region of memory
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*
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* @src: memory region to duplicate
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* @len: memory region length
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* @gfp: GFP mask to use
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*/
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void *kmemdup(const void *src, size_t len, gfp_t gfp)
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{
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void *p;
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p = ____kmalloc(len, gfp);
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if (p)
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memcpy(p, src, len);
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return p;
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}
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EXPORT_SYMBOL(kmemdup);
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/*
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* strndup_user - duplicate an existing string from user space
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*
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* @s: The string to duplicate
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* @n: Maximum number of bytes to copy, including the trailing NUL.
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*/
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char *strndup_user(const char __user *s, long n)
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{
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char *p;
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long length;
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length = strnlen_user(s, n);
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if (!length)
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return ERR_PTR(-EFAULT);
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if (length > n)
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return ERR_PTR(-EINVAL);
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p = kmalloc(length, GFP_KERNEL);
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if (!p)
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return ERR_PTR(-ENOMEM);
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if (copy_from_user(p, s, length)) {
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kfree(p);
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return ERR_PTR(-EFAULT);
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}
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p[length - 1] = '\0';
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return p;
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}
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EXPORT_SYMBOL(strndup_user);
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