atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable clip_entry.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
---
drivers/net/ethernet/chelsio/cxgb4/clip_tbl.c | 13 ++++++-------
drivers/net/ethernet/chelsio/cxgb4/clip_tbl.h | 4 +++-
2 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/drivers/net/ethernet/chelsio/cxgb4/clip_tbl.c b/drivers/net/ethernet/chelsio/cxgb4/clip_tbl.c
index 3103ef9..2900390 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/clip_tbl.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/clip_tbl.c
@@ -96,7 +96,8 @@ int cxgb4_clip_get(const struct net_device *dev, const u32 *lip, u8 v6)
if (!ret) {
ce = cte;
read_unlock_bh(&ctbl->lock);
- goto found;
+ refcount_inc(&ce->refcnt);
+ return 0;
}
}
read_unlock_bh(&ctbl->lock);
@@ -108,7 +109,7 @@ int cxgb4_clip_get(const struct net_device *dev, const u32 *lip, u8 v6)
list_del(&ce->list);
INIT_LIST_HEAD(&ce->list);
spin_lock_init(&ce->lock);
- atomic_set(&ce->refcnt, 0);
+ refcount_set(&ce->refcnt, 0);
atomic_dec(&ctbl->nfree);
list_add_tail(&ce->list, &ctbl->hash_list[hash]);
if (v6) {
@@ -138,9 +139,7 @@ int cxgb4_clip_get(const struct net_device *dev, const u32 *lip, u8 v6)
return -ENOMEM;
}
write_unlock_bh(&ctbl->lock);
-found:
- atomic_inc(&ce->refcnt);
-
+ refcount_set(&ce->refcnt, 1);
return 0;
}
EXPORT_SYMBOL(cxgb4_clip_get);
@@ -179,7 +178,7 @@ void cxgb4_clip_release(const struct net_device *dev, const u32 *lip, u8 v6)
found:
write_lock_bh(&ctbl->lock);
spin_lock_bh(&ce->lock);
- if (atomic_dec_and_test(&ce->refcnt)) {
+ if (refcount_dec_and_test(&ce->refcnt)) {
list_del(&ce->list);
INIT_LIST_HEAD(&ce->list);
list_add_tail(&ce->list, &ctbl->ce_free_head);
@@ -266,7 +265,7 @@ int clip_tbl_show(struct seq_file *seq, void *v)
ip[0] = '\0';
sprintf(ip, "%pISc", &ce->addr);
seq_printf(seq, "%-25s %u\n", ip,
- atomic_read(&ce->refcnt));
+ refcount_read(&ce->refcnt));
}
}
seq_printf(seq, "Free clip entries : %d\n", atomic_read(&ctbl->nfree));
diff --git a/drivers/net/ethernet/chelsio/cxgb4/clip_tbl.h b/drivers/net/ethernet/chelsio/cxgb4/clip_tbl.h
index 35eb43c..a0e0ae1 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/clip_tbl.h
+++ b/drivers/net/ethernet/chelsio/cxgb4/clip_tbl.h
@@ -10,9 +10,11 @@
* release for licensing terms and conditions.
*/
+#include <linux/refcount.h>
+
struct clip_entry {
spinlock_t lock; /* Hold while modifying clip reference */
- atomic_t refcnt;
+ refcount_t refcnt;
struct list_head list;
union {
struct sockaddr_in addr;
--
2.7.4
--
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