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drbd: narrow rcu_read_lock in drbd_sync_handshake

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[ Upstream commit d29e89e34952a9ad02c77109c71a80043544296e ]

So far there was the possibility that we called
genlmsg_new(GFP_NOIO)/mutex_lock() while holding an rcu_read_lock().

This included cases like:

drbd_sync_handshake (acquire the RCU lock)
  drbd_asb_recover_1p
    drbd_khelper
      drbd_bcast_event
        genlmsg_new(GFP_NOIO) --> may sleep

drbd_sync_handshake (acquire the RCU lock)
  drbd_asb_recover_1p
    drbd_khelper
      notify_helper
        genlmsg_new(GFP_NOIO) --> may sleep

drbd_sync_handshake (acquire the RCU lock)
  drbd_asb_recover_1p
    drbd_khelper
      notify_helper
        mutex_lock --> may sleep

While using GFP_ATOMIC whould have been possible in the first two cases,
the real fix is to narrow the rcu_read_lock.

Reported-by: Jia-Ju Bai <baijiaju1990@163.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Roland Kammerer <roland.kammerer@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Roland Kammerer 2018-12-20 17:23:28 +01:00 committed by Greg Kroah-Hartman
parent e1fe3f1e1c
commit 440a5c61c4
1 changed files with 6 additions and 5 deletions
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11
drivers/block/drbd/drbd_receiver.c
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@ -3361,7 +3361,7 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_peer_device *peer_device,
enum drbd_conns rv = C_MASK;
enum drbd_disk_state mydisk;
struct net_conf *nc;
int hg, rule_nr, rr_conflict, tentative;
int hg, rule_nr, rr_conflict, tentative, always_asbp;
mydisk = device->state.disk;
if (mydisk == D_NEGOTIATING)
@ -3412,8 +3412,12 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_peer_device *peer_device,
rcu_read_lock();
nc = rcu_dereference(peer_device->connection->net_conf);
always_asbp = nc->always_asbp;
rr_conflict = nc->rr_conflict;
tentative = nc->tentative;
rcu_read_unlock();
if (hg == 100 || (hg == -100 && nc->always_asbp)) {
if (hg == 100 || (hg == -100 && always_asbp)) {
int pcount = (device->state.role == R_PRIMARY)
+ (peer_role == R_PRIMARY);
int forced = (hg == -100);
@ -3452,9 +3456,6 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_peer_device *peer_device,
"Sync from %s node\n",
(hg < 0) ? "peer" : "this");
}
rr_conflict = nc->rr_conflict;
tentative = nc->tentative;
rcu_read_unlock();
if (hg == -100) {
/* FIXME this log message is not correct if we end up here