tcp repair: Fix unaligned access when repairing options (v2)

Don't pick __u8/__u16 values directly from raw pointers, but instead use
an array of structures of code:value pairs. This is OK, since the buffer
we take options from is not an skb memory, but a user-to-kernel one.

For those options which don't require any value now, require this to be
zero (for potential future extension of this API).

v2: Changed tcp_repair_opt to use two __u32-s as spotted by David Laight.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 21 insertions, 39 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index de6a238f0e1d..9670af341931 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2283,60 +2283,40 @@ static inline int tcp_can_repair_sock(struct sock *sk)
                 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_ESTABLISHED));
 }
 
-static int tcp_repair_options_est(struct tcp_sock *tp, char __user *optbuf, unsigned int len)
+static int tcp_repair_options_est(struct tcp_sock *tp,
+                struct tcp_repair_opt __user *optbuf, unsigned int len)
 {
-        /*
-         * Options are stored in CODE:VALUE form where CODE is 8bit and VALUE
-         * fits the respective TCPOLEN_ size
-         */
+        struct tcp_repair_opt opt;
 
-        while (len > 0) {
-                u8 opcode;
-
-                if (get_user(opcode, optbuf))
+        while (len >= sizeof(opt)) {
+                if (copy_from_user(&opt, optbuf, sizeof(opt)))
                         return -EFAULT;
 
                 optbuf++;
-                len--;
-
-                switch (opcode) {
-                case TCPOPT_MSS: {
-                        u16 in_mss;
+                len -= sizeof(opt);
 
-                        if (len < sizeof(in_mss))
-                                return -ENODATA;
-                        if (get_user(in_mss, optbuf))
-                                return -EFAULT;
-
-                        tp->rx_opt.mss_clamp = in_mss;
-
-                        optbuf += sizeof(in_mss);
-                        len -= sizeof(in_mss);
+                switch (opt.opt_code) {
+                case TCPOPT_MSS:
+                        tp->rx_opt.mss_clamp = opt.opt_val;
                         break;
-                }
-                case TCPOPT_WINDOW: {
-                        u8 wscale;
-
-                        if (len < sizeof(wscale))
-                                return -ENODATA;
-                        if (get_user(wscale, optbuf))
-                                return -EFAULT;
-
-                        if (wscale > 14)
+                case TCPOPT_WINDOW:
+                        if (opt.opt_val > 14)
                                 return -EFBIG;
 
-                        tp->rx_opt.snd_wscale = wscale;
-
-                        optbuf += sizeof(wscale);
-                        len -= sizeof(wscale);
+                        tp->rx_opt.snd_wscale = opt.opt_val;
                         break;
-                }
                 case TCPOPT_SACK_PERM:
+                        if (opt.opt_val != 0)
+                                return -EINVAL;
+
                         tp->rx_opt.sack_ok |= TCP_SACK_SEEN;
                         if (sysctl_tcp_fack)
                                 tcp_enable_fack(tp);
                         break;
                 case TCPOPT_TIMESTAMP:
+                        if (opt.opt_val != 0)
+                                return -EINVAL;
+
                         tp->rx_opt.tstamp_ok = 1;
                         break;
                 }
@@ -2557,7 +2537,9 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
                 if (!tp->repair)
                         err = -EINVAL;
                 else if (sk->sk_state == TCP_ESTABLISHED)
-                        err = tcp_repair_options_est(tp, optval, optlen);
+                        err = tcp_repair_options_est(tp,
+                                        (struct tcp_repair_opt __user *)optval,
+                                        optlen);
                 else
                         err = -EPERM;
                 break;