netdev - [PATCH net-next] rds: do not call ->conn_alloc with GFP

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Message-Id: <1518478238-164533-1-git-send-email-sowmini.varadhan@oracle.com>
Date:   Mon, 12 Feb 2018 15:30:38 -0800
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     sowmini.varadhan@...cle.com
Cc:     sowmini.varadhan@...cle.com, santosh.shilimkar@...cle.com,
        rds-devel@....oracle.com
Subject: [PATCH net-next] rds: do not call ->conn_alloc with GFP_KERNEL

Commit ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize
netns/module teardown and rds connection/workq management") adds an
rcu read critical section to __rds_conn_create. The memory allocations
in that critcal section need to use GFP_ATOMIC to avoid sleeping.

This patch was verified with syzkaller reproducer.

Reported-by: syzbot+a0564419941aaae3fe3c@...kaller.appspotmail.com
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
Fixes: ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize
netns/module teardown and rds connection/workq management")
---
 net/rds/connection.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/net/rds/connection.c b/net/rds/connection.c
index 94e190f..d0f5889 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -221,6 +221,8 @@ static void __rds_conn_path_init(struct rds_connection *conn,
 		conn->c_path[i].cp_index = i;
 	}
 	rcu_read_lock();
+	gfp &= ~GFP_KERNEL;
+	gfp |= GFP_ATOMIC;
 	if (rds_destroy_pending(conn))
 		ret = -ENETDOWN;
 	else
-- 
1.7.1