net: sock: move ->sk_shutdown out of bitfields.

->sk_shutdown bits share one bitfield with some other bits in sock struct,
such as ->sk_no_check_[r,t]x, ->sk_userlocks ...
sock_setsockopt() may write to these bits, while holding the socket lock.

In case of AF_UNIX sockets, we change ->sk_shutdown bits while holding only
unix_state_lock(). So concurrent setsockopt() and shutdown() may lead
to corrupting these bits.

Fix this by moving ->sk_shutdown bits out of bitfield into a separate byte.
This will not change the 'struct sock' size since ->sk_shutdown moved into
previously unused 16-bit hole.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/sock.h b/include/net/sock.h
index c9c8b19df27c558354687119db60c0716909ea3f..649d2a8c17fc36f04b4d317c41c33edd6cdfc8b7 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -382,8 +382,13 @@ struct sock {
        atomic_t                sk_omem_alloc;
        int                     sk_sndbuf;
        struct sk_buff_head     sk_write_queue;
+
+       /*
+        * Because of non atomicity rules, all
+        * changes are protected by socket lock.
+        */
        kmemcheck_bitfield_begin(flags);
-       unsigned int            sk_shutdown  : 2,
+       unsigned int            sk_padding : 2,
                                sk_no_check_tx : 1,
                                sk_no_check_rx : 1,
                                sk_userlocks : 4,
@@ -391,6 +396,7 @@ struct sock {
                                sk_type      : 16;
 #define SK_PROTOCOL_MAX U8_MAX
        kmemcheck_bitfield_end(flags);
+
        int                     sk_wmem_queued;
        gfp_t                   sk_allocation;
        u32                     sk_pacing_rate; /* bytes per second */
@@ -418,6 +424,7 @@ struct sock {
        struct timer_list       sk_timer;
        ktime_t                 sk_stamp;
        u16                     sk_tsflags;
+       u8                      sk_shutdown;
        u32                     sk_tskey;
        struct socket           *sk_socket;
        void                    *sk_user_data;