The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6f6f84aa215f7b6665ccbb937db50860f9ec2989 Mon Sep 17 00:00:00 2001 From: Zhang Xiaoxu zhangxiaoxu5@huawei.com Date: Sat, 21 May 2022 12:08:45 +0800 Subject: [PATCH] nfsd: Fix null-ptr-deref in nfsd_fill_super()

KASAN report null-ptr-deref as follows:

BUG: KASAN: null-ptr-deref in nfsd_fill_super+0xc6/0xe0 [nfsd] Write of size 8 at addr 000000000000005d by task a.out/852

CPU: 7 PID: 852 Comm: a.out Not tainted 5.18.0-rc7-dirty #66 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x34/0x44 kasan_report+0xab/0x120 ? nfsd_mkdir+0x71/0x1c0 [nfsd] ? nfsd_fill_super+0xc6/0xe0 [nfsd] nfsd_fill_super+0xc6/0xe0 [nfsd] ? nfsd_mkdir+0x1c0/0x1c0 [nfsd] get_tree_keyed+0x8e/0x100 vfs_get_tree+0x41/0xf0 __do_sys_fsconfig+0x590/0x670 ? fscontext_read+0x180/0x180 ? anon_inode_getfd+0x4f/0x70 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae

This can be reproduce by concurrent operations: 1. fsopen(nfsd)/fsconfig 2. insmod/rmmod nfsd

Since the nfsd file system is registered before than nfsd_net allocated, the caller may get the file_system_type and use the nfsd_net before it allocated, then null-ptr-deref occurred.

So init_nfsd() should call register_filesystem() last.

Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") Signed-off-by: Zhang Xiaoxu zhangxiaoxu5@huawei.com Signed-off-by: Chuck Lever chuck.lever@oracle.com

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index 55949e60897d..0621c2faf242 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1535,25 +1535,25 @@ static int __init init_nfsd(void) retval = create_proc_exports_entry(); if (retval) goto out_free_lockd; - retval = register_filesystem(&nfsd_fs_type); - if (retval) - goto out_free_exports; retval = register_pernet_subsys(&nfsd_net_ops); if (retval < 0) - goto out_free_filesystem; + goto out_free_exports; retval = register_cld_notifier(); if (retval) goto out_free_subsys; retval = nfsd4_create_laundry_wq(); + if (retval) + goto out_free_cld; + retval = register_filesystem(&nfsd_fs_type); if (retval) goto out_free_all; return 0; out_free_all: + nfsd4_destroy_laundry_wq(); +out_free_cld: unregister_cld_notifier(); out_free_subsys: unregister_pernet_subsys(&nfsd_net_ops); -out_free_filesystem: - unregister_filesystem(&nfsd_fs_type); out_free_exports: remove_proc_entry("fs/nfs/exports", NULL); remove_proc_entry("fs/nfs", NULL); @@ -1571,6 +1571,7 @@ static int __init init_nfsd(void)

static void __exit exit_nfsd(void) { + unregister_filesystem(&nfsd_fs_type); nfsd4_destroy_laundry_wq(); unregister_cld_notifier(); unregister_pernet_subsys(&nfsd_net_ops); @@ -1581,7 +1582,6 @@ static void __exit exit_nfsd(void) nfsd_lockd_shutdown(); nfsd4_free_slabs(); nfsd4_exit_pnfs(); - unregister_filesystem(&nfsd_fs_type); }

MODULE_AUTHOR("Olaf Kirch okir@monad.swb.de");