dlm: fix plock use-after-free
Fix a regression from the original addition of nfs lock support
586759f03e2e9031ac5589912a51a909ed53c30a. When a synchronous
(non-nfs) plock completes, the waiting thread will wake up and
free the op struct. This races with the user thread in
dev_write() which goes on to read the op's callback field to
check if the lock is async and needs a callback. This check
can happen on the freed op. The fix is to note the callback
value before the op can be freed.
Signed-off-by: David Teigland <teigland@redhat.com>
diff --git a/fs/dlm/plock.c b/fs/dlm/plock.c
index 894a32d..16f682e 100644
--- a/fs/dlm/plock.c
+++ b/fs/dlm/plock.c
@@ -353,7 +353,7 @@
{
struct dlm_plock_info info;
struct plock_op *op;
- int found = 0;
+ int found = 0, do_callback = 0;
if (count != sizeof(info))
return -EINVAL;
@@ -366,21 +366,24 @@
spin_lock(&ops_lock);
list_for_each_entry(op, &recv_list, list) {
- if (op->info.fsid == info.fsid && op->info.number == info.number &&
+ if (op->info.fsid == info.fsid &&
+ op->info.number == info.number &&
op->info.owner == info.owner) {
+ struct plock_xop *xop = (struct plock_xop *)op;
list_del_init(&op->list);
- found = 1;
- op->done = 1;
memcpy(&op->info, &info, sizeof(info));
+ if (xop->callback)
+ do_callback = 1;
+ else
+ op->done = 1;
+ found = 1;
break;
}
}
spin_unlock(&ops_lock);
if (found) {
- struct plock_xop *xop;
- xop = (struct plock_xop *)op;
- if (xop->callback)
+ if (do_callback)
dlm_plock_callback(op);
else
wake_up(&recv_wq);