[SRU][J][PATCH 1/3] SUNRPC: Check if the xprt is connected before handling sysfs reads

[Matthew Ruffell]

From: Anna Schumaker <Anna.Schumaker at Netapp.com>

BugLink: https://bugs.launchpad.net/bugs/2149767

xprts don't immediately reconnect when changing the "dstaddr" property,
instead this gets handled the next time an operation uses the transport.
This could lead to NULL pointer dereferences when trying to read sysfs
files between the disconnect and reconnect operations. Fix this by
returning an error if the xprt is not connected.

Signed-off-by: Anna Schumaker <Anna.Schumaker at Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust at hammerspace.com>
(cherry picked from commit 17f09d3f619a7ad2d2b021b4e5246f08225b1b0f)
Signed-off-by: Matthew Ruffell <matthew.ruffell at canonical.com>
---
 net/sunrpc/sysfs.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/sunrpc/sysfs.c b/net/sunrpc/sysfs.c
index 55da1b627a7d..66785d1f90b8 100644
--- a/net/sunrpc/sysfs.c
+++ b/net/sunrpc/sysfs.c
@@ -109,8 +109,10 @@ static ssize_t rpc_sysfs_xprt_srcaddr_show(struct kobject *kobj,
 	struct sock_xprt *sock;
 	ssize_t ret = -1;
 
-	if (!xprt)
-		return 0;
+	if (!xprt || !xprt_connected(xprt)) {
+		xprt_put(xprt);
+		return -ENOTCONN;
+	}
 
 	sock = container_of(xprt, struct sock_xprt, xprt);
 	if (kernel_getsockname(sock->sock, (struct sockaddr *)&saddr) < 0)
@@ -129,8 +131,10 @@ static ssize_t rpc_sysfs_xprt_info_show(struct kobject *kobj,
 	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
 	ssize_t ret;
 
-	if (!xprt)
-		return 0;
+	if (!xprt || !xprt_connected(xprt)) {
+		xprt_put(xprt);
+		return -ENOTCONN;
+	}
 
 	ret = sprintf(buf, "last_used=%lu\ncur_cong=%lu\ncong_win=%lu\n"
 		       "max_num_slots=%u\nmin_num_slots=%u\nnum_reqs=%u\n"
-- 
2.53.0