[PATCH AUTOSEL 5.16 13/52] sunrpc: Fix potential race conditions in rpc_sysfs_xprt_state_change()

Sasha Levin
2022-02-03T20:30:47Z

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

[ Upstream commit 1a48db3fef499f615b56093947ec4b0d3d8e3021 ]

We need to use test_and_set_bit() when changing xprt state flags to
avoid potentially getting xps->xps_nactive out of sync.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sunrpc/sysfs.c | 35 +++++++++++++++++++----------------
1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/net/sunrpc/sysfs.c b/net/sunrpc/sysfs.c
index 77e7d011c1ab1..8f309bcdf84fe 100644
--- a/net/sunrpc/sysfs.c
+++ b/net/sunrpc/sysfs.c
@@ -309,25 +309,28 @@ static ssize_t rpc_sysfs_xprt_state_change(struct kobject *kobj,
goto release_tasks;
}
if (offline) {
- set_bit(XPRT_OFFLINE, &xprt->state);
- spin_lock(&xps->xps_lock);
- xps->xps_nactive--;
- spin_unlock(&xps->xps_lock);
+ if (!test_and_set_bit(XPRT_OFFLINE, &xprt->state)) {
+ spin_lock(&xps->xps_lock);
+ xps->xps_nactive--;
+ spin_unlock(&xps->xps_lock);
+ }
} else if (online) {
- clear_bit(XPRT_OFFLINE, &xprt->state);
- spin_lock(&xps->xps_lock);
- xps->xps_nactive++;
- spin_unlock(&xps->xps_lock);
+ if (test_and_clear_bit(XPRT_OFFLINE, &xprt->state)) {
+ spin_lock(&xps->xps_lock);
+ xps->xps_nactive++;
+ spin_unlock(&xps->xps_lock);
+ }
} else if (remove) {
if (test_bit(XPRT_OFFLINE, &xprt->state)) {
- set_bit(XPRT_REMOVE, &xprt->state);
- xprt_force_disconnect(xprt);
- if (test_bit(XPRT_CONNECTED, &xprt->state)) {
- if (!xprt->sending.qlen &&
- !xprt->pending.qlen &&
- !xprt->backlog.qlen &&
- !atomic_long_read(&xprt->queuelen))
- rpc_xprt_switch_remove_xprt(xps, xprt);
+ if (!test_and_set_bit(XPRT_REMOVE, &xprt->state)) {
+ xprt_force_disconnect(xprt);
+ if (test_bit(XPRT_CONNECTED, &xprt->state)) {
+ if (!xprt->sending.qlen &&
+ !xprt->pending.qlen &&
+ !xprt->backlog.qlen &&
+ !atomic_long_read(&xprt->queuelen))
+ rpc_xprt_switch_remove_xprt(xps, xprt);
+ }
}
} else {
count = -EINVAL;
--
2.34.1