netdev - [PATCH v3 net-next] rds: do not call ->conn_alloc with GFP

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Message-Id: <1518543976-167907-1-git-send-email-sowmini.varadhan@oracle.com>
Date:   Tue, 13 Feb 2018 09:46:16 -0800
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     sowmini.varadhan@...cle.com
Cc:     sowmini.varadhan@...cle.com, santosh.shilimkar@...cle.com
Subject: [PATCH v3 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 __rd_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
Fixes: ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize
       netns/module teardown and rds connection/workq management")
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
---
v2: do not over-engineer. Keep the gfp arg to ->conn_alloc simple.
v3: resending since previous attempt did not show up in patch queue.

 net/rds/connection.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/rds/connection.c b/net/rds/connection.c
index 94e190f..2da3176 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -224,7 +224,7 @@ static void __rds_conn_path_init(struct rds_connection *conn,
 	if (rds_destroy_pending(conn))
 		ret = -ENETDOWN;
 	else
-		ret = trans->conn_alloc(conn, gfp);
+		ret = trans->conn_alloc(conn, GFP_ATOMIC);
 	if (ret) {
 		rcu_read_unlock();
 		kfree(conn->c_path);
-- 
1.7.1