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authorPekka Enberg <penberg@cs.helsinki.fi>2008-07-26 17:49:33 -0700
committerDavid S. Miller <davem@davemloft.net>2008-07-26 17:49:33 -0700
commit93bc4e89c260d91576840c4881d1066d84ccd422 (patch)
tree456176a054fc9a3fed18ac6ce50c7a34a86c5808 /mm/util.c
parent3918fed5f31213067c1c345bd904e1ea369e6819 (diff)
downloadlinux-93bc4e89c260d91576840c4881d1066d84ccd422.tar.gz
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>
Diffstat (limited to 'mm/util.c')
-rw-r--r--mm/util.c44
1 files changed, 34 insertions, 10 deletions
diff --git a/mm/util.c b/mm/util.c
index 8f18683825b..6ef9e9943f6 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -68,25 +68,22 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
EXPORT_SYMBOL(kmemdup);
/**
- * krealloc - reallocate memory. The contents will remain unchanged.
+ * __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.
*
- * The contents of the object pointed to are preserved up to the
- * lesser of the new and old sizes. If @p is %NULL, krealloc()
- * behaves exactly like kmalloc(). If @size is 0 and @p is not a
- * %NULL pointer, the object pointed to is freed.
+ * 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 *__krealloc(const void *p, size_t new_size, gfp_t flags)
{
void *ret;
size_t ks = 0;
- if (unlikely(!new_size)) {
- kfree(p);
+ if (unlikely(!new_size))
return ZERO_SIZE_PTR;
- }
if (p)
ks = ksize(p);
@@ -95,10 +92,37 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags)
return (void *)p;
ret = kmalloc_track_caller(new_size, flags);
- if (ret && p) {
+ 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.
+ * @new_size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate.
+ *
+ * The contents of the object pointed to are preserved up to the
+ * lesser of the new and old sizes. If @p is %NULL, krealloc()
+ * behaves exactly like kmalloc(). If @size is 0 and @p is not a
+ * %NULL pointer, the object pointed to is freed.
+ */
+void *krealloc(const void *p, size_t new_size, gfp_t flags)
+{
+ void *ret;
+
+ if (unlikely(!new_size)) {
kfree(p);
+ return ZERO_SIZE_PTR;
}
+
+ ret = __krealloc(p, new_size, flags);
+ if (ret && p != ret)
+ kfree(p);
+
return ret;
}
EXPORT_SYMBOL(krealloc);