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netfilter: fix double-free and use-after free 

As suggested by Patrick McHardy, introduce a __krealloc() that doesn't
free the original buffer to fix a double-free and use-after-free bug
introduced by me in netfilter that uses RCU.

Reported-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Tested-by: Dieter Ries <clip2@gmx.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Pekka Enberg 2008-07-26 17:49:33 -07:00 committed by David S. Miller
parent 3918fed5f3
commit 93bc4e89c2
3 changed files with 37 additions and 12 deletions
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1
include/linux/slab.h
View File

@ -96,6 +96,7 @@ int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr);
/*
* Common kmalloc functions provided by all allocators
*/
void * __must_check __krealloc(const void *, size_t, gfp_t);
void * __must_check krealloc(const void *, size_t, gfp_t);
void kfree(const void *);
size_t ksize(const void *);

46
mm/util.c
View File

@ -67,6 +67,38 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
}
EXPORT_SYMBOL(kmemdup);
/**
* __krealloc - like krealloc() but don't free @p.
* @p: object to reallocate memory for.
* @new_size: how many bytes of memory are required.
* @flags: the type of memory to allocate.
*
* This function is like krealloc() except it never frees the originally
* allocated buffer. Use this if you don't want to free the buffer immediately
* like, for example, with RCU.
*/
void *__krealloc(const void *p, size_t new_size, gfp_t flags)
{
void *ret;
size_t ks = 0;
if (unlikely(!new_size))
return ZERO_SIZE_PTR;
if (p)
ks = ksize(p);
if (ks >= new_size)
return (void *)p;
ret = kmalloc_track_caller(new_size, flags);
if (ret && p)
memcpy(ret, p, ks);
return ret;
}
EXPORT_SYMBOL(__krealloc);
/**
* krealloc - reallocate memory. The contents will remain unchanged.
* @p: object to reallocate memory for.
@ -81,24 +113,16 @@ EXPORT_SYMBOL(kmemdup);
void *krealloc(const void *p, size_t new_size, gfp_t flags)
{
void *ret;
size_t ks = 0;
if (unlikely(!new_size)) {
kfree(p);
return ZERO_SIZE_PTR;
}
if (p)
ks = ksize(p);
if (ks >= new_size)
return (void *)p;
ret = kmalloc_track_caller(new_size, flags);
if (ret && p) {
memcpy(ret, p, ks);
ret = __krealloc(p, new_size, flags);
if (ret && p != ret)
kfree(p);
}
return ret;
}
EXPORT_SYMBOL(krealloc);

2
net/netfilter/nf_conntrack_extend.c
View File

@ -95,7 +95,7 @@ void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
newlen = newoff + t->len;
rcu_read_unlock();
new = krealloc(ct->ext, newlen, gfp);
new = __krealloc(ct->ext, newlen, gfp);
if (!new)
return NULL;