linux-kernel - [PATCH 3.12 79/86] RDS: Fix the atomicity for congestion map update

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Date:   Thu,  4 May 2017 11:04:44 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        "santosh.shilimkar@...cle.com" <santosh.shilimkar@...cle.com>,
        Wengang Wang <wen.gang.wang@...cle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Julia Lawall <julia.lawall@...6.fr>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 79/86] RDS: Fix the atomicity for congestion map update

From: "santosh.shilimkar@...cle.com" <santosh.shilimkar@...cle.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit e47db94e10447fc467777a40302f2b393e9af2fa upstream.

Two different threads with different rds sockets may be in
rds_recv_rcvbuf_delta() via receive path. If their ports
both map to the same word in the congestion map, then
using non-atomic ops to update it could cause the map to
be incorrect. Lets use atomics to avoid such an issue.

Full credit to Wengang <wen.gang.wang@...cle.com> for
finding the issue, analysing it and also pointing out
to offending code with spin lock based fix.

Reviewed-by: Leon Romanovsky <leon@...n.nu>
Signed-off-by: Wengang Wang <wen.gang.wang@...cle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Cc: Julia Lawall <julia.lawall@...6.fr>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 net/rds/cong.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/rds/cong.c b/net/rds/cong.c
index e5b65acd650b..cec4c4e6d905 100644
--- a/net/rds/cong.c
+++ b/net/rds/cong.c
@@ -285,7 +285,7 @@ void rds_cong_set_bit(struct rds_cong_map *map, __be16 port)
 	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
 	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
 
-	__set_bit_le(off, (void *)map->m_page_addrs[i]);
+	set_bit_le(off, (void *)map->m_page_addrs[i]);
 }
 
 void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port)
@@ -299,7 +299,7 @@ void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port)
 	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
 	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
 
-	__clear_bit_le(off, (void *)map->m_page_addrs[i]);
+	clear_bit_le(off, (void *)map->m_page_addrs[i]);
 }
 
 static int rds_cong_test_bit(struct rds_cong_map *map, __be16 port)
-- 
2.12.2