[PATCH] bridge: fix possible overflow in get_fdb_entries

Make sure to properly clamp maxnum to avoid overflow

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Acked-by: Eugene Teo <eteo@redhat.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 4 deletions

diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index 4e4119a12139..4c61a7e0a86e 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -58,12 +58,13 @@ static int get_fdb_entries(struct net_bridge *br, void __user *userbuf,
 {
         int num;
         void *buf;
-        size_t size = maxnum * sizeof(struct __fdb_entry);
+        size_t size;
 
-        if (size > PAGE_SIZE) {
-                size = PAGE_SIZE;
+        /* Clamp size to PAGE_SIZE, test maxnum to avoid overflow */
+        if (maxnum > PAGE_SIZE/sizeof(struct __fdb_entry))
                 maxnum = PAGE_SIZE/sizeof(struct __fdb_entry);
-        }
+
+        size = maxnum * sizeof(struct __fdb_entry);
 
         buf = kmalloc(size, GFP_USER);
         if (!buf)