CVE-2024-53167

In the Linux kernel, the following vulnerability has been resolved:

nfs/blocklayout: Don't attempt unregister for invalid block device

Since commit d869da91cccb ("nfs/blocklayout: Fix premature PR key

unregistration") an unmount of a pNFS SCSI layout-enabled NFS may

dereference a NULL block_device in:

bl_unregister_scsi+0x16/0xe0 [blocklayoutdriver]

bl_free_device+0x70/0x80 [blocklayoutdriver]

bl_free_deviceid_node+0x12/0x30 [blocklayoutdriver]

nfs4_put_deviceid_node+0x60/0xc0 [nfsv4]

nfs4_deviceid_purge_client+0x132/0x190 [nfsv4]

unset_pnfs_layoutdriver+0x59/0x60 [nfsv4]

nfs4_destroy_server+0x36/0x70 [nfsv4]

nfs_free_server+0x23/0xe0 [nfs]

deactivate_locked_super+0x30/0xb0

cleanup_mnt+0xba/0x150

task_work_run+0x59/0x90

syscall_exit_to_user_mode+0x217/0x220

do_syscall_64+0x8e/0x160

This happens because even though we were able to create the

nfs4_deviceid_node, the lookup for the device was unable to attach the

block device to the pnfs_block_dev.

If we never found a block device to register, we can avoid this case with

the PNFS_BDEV_REGISTERED flag. Move the deref behind the test for the

flag.