unix: properly account for FDs passed over unix sockets

[sagit-ice-cold/kernel_xiaomi_msm8998.git] / net / unix / af_unix.c

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index ef05cd9..e3f85bc 100644 (file)
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1513,6 +1513,21 @@ static void unix_destruct_scm(struct sk_buff *skb)
        sock_wfree(skb);
 }
 
+/*
+ * The "user->unix_inflight" variable is protected by the garbage
+ * collection lock, and we just read it locklessly here. If you go
+ * over the limit, there might be a tiny race in actually noticing
+ * it across threads. Tough.
+ */
+static inline bool too_many_unix_fds(struct task_struct *p)
+{
+       struct user_struct *user = current_user();
+
+       if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
+               return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
+       return false;
+}
+
 #define MAX_RECURSION_LEVEL 4
 
 static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
@@ -1521,6 +1536,9 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
        unsigned char max_level = 0;
        int unix_sock_count = 0;
 
+       if (too_many_unix_fds(current))
+               return -ETOOMANYREFS;
+
        for (i = scm->fp->count - 1; i >= 0; i--) {
                struct sock *sk = unix_get_socket(scm->fp->fp[i]);
 
@@ -1542,10 +1560,8 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
        if (!UNIXCB(skb).fp)
                return -ENOMEM;
 
-       if (unix_sock_count) {
-               for (i = scm->fp->count - 1; i >= 0; i--)
-                       unix_inflight(scm->fp->fp[i]);
-       }
+       for (i = scm->fp->count - 1; i >= 0; i--)
+               unix_inflight(scm->fp->fp[i]);
        return max_level;
 }