dlm: prevent NPD when writing a positive value to event_done

do_uevent returns the value written to event_done. In case it is a
positive value, new_lockspace would undo all the work, and lockspace
would not be set. __dlm_new_lockspace, however, would treat that
positive value as a success due to commit 8511a2728ab8 ("dlm: fix use
count with multiple joins").

Down the line, device_create_lockspace would pass that NULL lockspace to
dlm_find_lockspace_local, leading to a NULL pointer dereference.

Treating such positive values as successes prevents the problem. Given
this has been broken for so long, this is unlikely to break userspace
expectations.

Fixes: 8511a2728ab8 ("dlm: fix use count with multiple joins")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: David Teigland <teigland@redhat.com>

diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index 8afac6e2dff0029291102d3c66f09352286ec8b2..1929327ffbe1cf5775097e20ad1ab79824ddf059 100644 (file)
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -576,7 +576,7 @@ static int new_lockspace(const char *name, const char *cluster,
           lockspace to start running (via sysfs) in dlm_ls_start(). */
 
        error = do_uevent(ls, 1);
-       if (error)
+       if (error < 0)
                goto out_recoverd;
 
        /* wait until recovery is successful or failed */