4.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Howells dhowells@redhat.com
[ Upstream commit 660625922b3d9fcb376e5870299bc5c1086e1d32 ]
AFS server records get removed from the net->fs_servers tree when they're deleted, but not from the net->fs_addresses{4,6} lists, which can lead to an oops in afs_find_server() when a server record has been removed, for instance during rmmod.
Fix this by deleting the record from the by-address lists before posting it for RCU destruction.
The reason this hasn't been noticed before is that the fileserver keeps probing the local cache manager, thereby keeping the service record alive, so the oops would only happen when a fileserver eventually gets bored and stops pinging or if the module gets rmmod'd and a call comes in from the fileserver during the window between the server records being destroyed and the socket being closed.
The oops looks something like:
BUG: unable to handle kernel NULL pointer dereference at 000000000000001c ... Workqueue: kafsd afs_process_async_call [kafs] RIP: 0010:afs_find_server+0x271/0x36f [kafs] ... Call Trace: afs_deliver_cb_init_call_back_state3+0x1f2/0x21f [kafs] afs_deliver_to_call+0x1ee/0x5e8 [kafs] afs_process_async_call+0x5b/0xd0 [kafs] process_one_work+0x2c2/0x504 worker_thread+0x1d4/0x2ac kthread+0x11f/0x127 ret_from_fork+0x24/0x30
Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation") Signed-off-by: David Howells dhowells@redhat.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/afs/server.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/fs/afs/server.c +++ b/fs/afs/server.c @@ -426,8 +426,15 @@ static void afs_gc_servers(struct afs_ne } write_sequnlock(&net->fs_lock);
- if (deleted) + if (deleted) { + write_seqlock(&net->fs_addr_lock); + if (!hlist_unhashed(&server->addr4_link)) + hlist_del_rcu(&server->addr4_link); + if (!hlist_unhashed(&server->addr6_link)) + hlist_del_rcu(&server->addr6_link); + write_sequnlock(&net->fs_addr_lock); afs_destroy_server(net, server); + } } }