From 93bc4e89c260d91576840c4881d1066d84ccd422 Mon Sep 17 00:00:00 2001
From: Pekka Enberg <penberg@cs.helsinki.fi>
Date: Sat, 26 Jul 2008 17:49:33 -0700
Subject: [PATCH] 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>
---
include/linux/slab.h | 1 +
mm/util.c | 46 ++++++++++++++++++++++-------
net/netfilter/nf_conntrack_extend.c | 2 +-
3 files changed, 37 insertions(+), 12 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 9aa90a6f20e0..be6f1d40b66a 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -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 *);
diff --git a/mm/util.c b/mm/util.c
index 8f18683825bc..6ef9e9943f62 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -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);
diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
index 3469bc71a385..c956ef7eeecb 100644
--- a/net/netfilter/nf_conntrack_extend.c
+++ b/net/netfilter/nf_conntrack_extend.c
@@ -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;