If the CM ID is destroyed while the CM event for multicast creating is still queued the cancel_work_sync() will prevent the work from running which also prevents destroying the ah_attr. This leaks a refcount and triggers a WARN:

GID entry ref leak for dev syz1 index 2 ref=573 WARNING: CPU: 1 PID: 655 at drivers/infiniband/core/cache.c:809 release_gid_table drivers/infiniband/core/cache.c:806 [inline] WARNING: CPU: 1 PID: 655 at drivers/infiniband/core/cache.c:809 gid_table_release_one+0x284/0x3cc drivers/infiniband/core/cache.c:886

Destroy the ah_attr after canceling the work, it is safe to call this twice.

Cc: stable@vger.kernel.org Fixes: fe454dc31e84 ("RDMA/ucma: Fix use-after-free bug in ucma_create_uevent") Reported-by: syzbot+b0da83a6c0e2e2bddbd4@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68232e7b.050a0220.f2294.09f6.GAE@google.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com --- drivers/infiniband/core/cma.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c index 95e89f5c147c2c..4f5fd47086ab90 100644 --- a/drivers/infiniband/core/cma.c +++ b/drivers/infiniband/core/cma.c @@ -2031,6 +2031,8 @@ static void destroy_mc(struct rdma_id_private *id_priv, dev_put(ndev);

cancel_work_sync(&mc->iboe_join.work); + if (event->event == RDMA_CM_EVENT_MULTICAST_JOIN) + rdma_destroy_ah_attr(&event->param.ud.ah_attr); } kfree(mc); }

base-commit: 3fbaef0942719187f3396bfd0c780d55d35e0980