[Devel] [PATCH rh7] ms/net: sock: move ->sk_shutdown out of bitfields.

[Andrey Ryabinin]

->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.

https://jira.sw.ru/browse/PSBM-47023

Link: http://lkml.kernel.org/g/1463588367-16310-1-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
Suggested-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
Acked-by: Eric Dumazet <edumazet at google.com>
---
 include/net/sock.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index b940aa5..ccaacb6 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -370,8 +370,13 @@ 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,
 #ifdef __GENKSYMS__
 				sk_no_check : 2,
 #else
@@ -382,6 +387,7 @@ struct sock {
 				sk_protocol  : 8,
 				sk_type      : 16;
 	kmemcheck_bitfield_end(flags);
+
 	int			sk_wmem_queued;
 	gfp_t			sk_allocation;
 	u32			sk_pacing_rate; /* bytes per second */
@@ -390,6 +396,7 @@ struct sock {
 	int			sk_gso_type;
 	unsigned int		sk_gso_max_size;
 	u16			sk_gso_max_segs;
+	u8			sk_shutdown;
 	int			sk_rcvlowat;
 	unsigned long	        sk_lingertime;
 	struct sk_buff_head	sk_error_queue;
-- 
2.7.3