[PATCH 9/9] net, ipv4: convert fib_info.fib_clntref from atomic_t to refcount_t

From: Elena Reshetova
Date: Thu Mar 16 2017 - 14:24:26 EST


refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
---
include/net/ip_fib.h | 7 ++++---
net/ipv4/fib_semantics.c | 2 +-
net/ipv4/fib_trie.c | 2 +-
3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 368bb40..55d2694 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -23,6 +23,7 @@
#include <net/inetpeer.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
+#include <linux/refcount.h>

struct fib_config {
u8 fc_dst_len;
@@ -105,7 +106,7 @@ struct fib_info {
struct hlist_node fib_lhash;
struct net *fib_net;
int fib_treeref;
- atomic_t fib_clntref;
+ refcount_t fib_clntref;
unsigned int fib_flags;
unsigned char fib_dead;
unsigned char fib_protocol;
@@ -407,12 +408,12 @@ void free_fib_info(struct fib_info *fi);

static inline void fib_info_hold(struct fib_info *fi)
{
- atomic_inc(&fi->fib_clntref);
+ refcount_inc(&fi->fib_clntref);
}

static inline void fib_info_put(struct fib_info *fi)
{
- if (atomic_dec_and_test(&fi->fib_clntref))
+ if (refcount_dec_and_test(&fi->fib_clntref))
free_fib_info(fi);
}

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 317026a..9c361bd 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -1174,7 +1174,7 @@ struct fib_info *fib_create_info(struct fib_config *cfg)
}

fi->fib_treeref++;
- atomic_inc(&fi->fib_clntref);
+ refcount_set(&fi->fib_clntref, 1);
spin_lock_bh(&fib_info_lock);
hlist_add_head(&fi->fib_hash,
&fib_info_hash[fib_info_hashfn(fi)]);
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 2f0d823..d3bbe6e 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1543,7 +1543,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp,
}

if (!(fib_flags & FIB_LOOKUP_NOREF))
- atomic_inc(&fi->fib_clntref);
+ refcount_inc(&fi->fib_clntref);

res->prefixlen = KEYLENGTH - fa->fa_slen;
res->nh_sel = nhsel;
--
2.7.4