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nbd: call genl_unregister_family() first in nbd_cleanup()

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[ Upstream commit 06c4da89c24e7023ea448cadf8e9daf06a0aae6e ]

Otherwise there may be race between module removal and the handling of
netlink command, which can lead to the oops as shown below:

  BUG: kernel NULL pointer dereference, address: 0000000000000098
  Oops: 0002 [#1] SMP PTI
  CPU: 1 PID: 31299 Comm: nbd-client Tainted: G            E     5.14.0-rc4
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
  RIP: 0010:down_write+0x1a/0x50
  Call Trace:
   start_creating+0x89/0x130
   debugfs_create_dir+0x1b/0x130
   nbd_start_device+0x13d/0x390 [nbd]
   nbd_genl_connect+0x42f/0x748 [nbd]
   genl_family_rcv_msg_doit.isra.0+0xec/0x150
   genl_rcv_msg+0xe5/0x1e0
   netlink_rcv_skb+0x55/0x100
   genl_rcv+0x29/0x40
   netlink_unicast+0x1a8/0x250
   netlink_sendmsg+0x21b/0x430
   ____sys_sendmsg+0x2a4/0x2d0
   ___sys_sendmsg+0x81/0xc0
   __sys_sendmsg+0x62/0xb0
   __x64_sys_sendmsg+0x1f/0x30
   do_syscall_64+0x3b/0xc0
   entry_SYSCALL_64_after_hwframe+0x44/0xae
  Modules linked in: nbd(E-)

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20220521073749.3146892-2-yukuai3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Yu Kuai 2022-05-21 15:37:44 +08:00 committed by Greg Kroah-Hartman
parent cb8da20d71
commit c0868f6e72
1 changed files with 6 additions and 1 deletions
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7
drivers/block/nbd.c
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@ -2461,6 +2461,12 @@ static void __exit nbd_cleanup(void)
struct nbd_device *nbd;
LIST_HEAD(del_list);
/*
* Unregister netlink interface prior to waiting
* for the completion of netlink commands.
*/
genl_unregister_family(&nbd_genl_family);
nbd_dbg_close();
mutex_lock(&nbd_index_mutex);
@ -2476,7 +2482,6 @@ static void __exit nbd_cleanup(void)
}
idr_destroy(&nbd_index_idr);
genl_unregister_family(&nbd_genl_family);
unregister_blkdev(NBD_MAJOR, "nbd");
}