ipv6: use READ_ONCE() for inet->hdrincl as in ipv4

[ Upstream commit 59e3e4b52663a9d97efbce7307f62e4bc5c9ce91 ]

As it was done in commit 8f659a03a0ba ("net: ipv4: fix for a race
condition in raw_sendmsg") and commit 20b50d79974e ("net: ipv4: emulate
READ_ONCE() on ->hdrincl bit-field in raw_sendmsg()") for ipv4, copy the
value of inet->hdrincl in a local variable, to avoid introducing a race
condition in the next commit.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 5833d4a..2133f26 100644 (file)
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -782,6 +782,7 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
        struct flowi6 fl6;
        struct ipcm6_cookie ipc6;
        int addr_len = msg->msg_namelen;
+       int hdrincl;
        u16 proto;
        int err;
 
@@ -795,6 +796,13 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
        if (msg->msg_flags & MSG_OOB)
                return -EOPNOTSUPP;
 
+       /* hdrincl should be READ_ONCE(inet->hdrincl)
+        * but READ_ONCE() doesn't work with bit fields.
+        * Doing this indirectly yields the same result.
+        */
+       hdrincl = inet->hdrincl;
+       hdrincl = READ_ONCE(hdrincl);
+
        /*
         *      Get and verify the address.
         */
@@ -907,7 +915,7 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
                fl6.flowi6_oif = np->ucast_oif;
        security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));
 
-       if (inet->hdrincl)
+       if (hdrincl)
                fl6.flowi6_flags |= FLOWI_FLAG_KNOWN_NH;
 
        if (ipc6.tclass < 0)
@@ -930,7 +938,7 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
                goto do_confirm;
 
 back_from_confirm:
-       if (inet->hdrincl)
+       if (hdrincl)
                err = rawv6_send_hdrinc(sk, msg, len, &fl6, &dst,
                                        msg->msg_flags, &ipc6.sockc);
        else {