From nobody Sat Feb 7 08:13:56 2026 Received: from m16.mail.163.com (m16.mail.163.com [117.135.210.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF9B5126BF7; Wed, 28 Jan 2026 08:34:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.4 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769589268; cv=none; b=d8YIMSYn8WBpB9CJM6O81zJEaIg5vyaC5QJImOqe7uZehgFNFOkz1iTbafzzg6kJtUi/cj9Wp4/dEYhzT7EM2lY2rayeUVMZmMnEMNE2Q8csNZ4/Oa1H19uU2HnKYlx/k+K1wej28pDIkPJkCqF4E0XfBsJ9cymhAcyWwy06/Q0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769589268; c=relaxed/simple; bh=TqTACZK3OBk0pUKATcGn6BWuIvsrzEnP8cmnnv4HbA4=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=gGdKR2KBUdOuG2AcFPw55CjDpYqVNjgBqM93TvavEsiprqwNFBzw9/SYZ9l14MMICdtvqNf7Nu1r+ovJK5q/LThbAm14LXdO5eqtdiFLUTABGsZehiZO7kKEBuJ62rz9Ana1UJwjMdKHIjU1MJTQdoRlHTkkZNpnUmg6XdnJMC0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=kcT79GNB; arc=none smtp.client-ip=117.135.210.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="kcT79GNB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=uT jphfMycXIDAOSyBJrJwCxg71drU2hua4RoaxHISfk=; b=kcT79GNB+E0QAEvv2N 8LSYl25SBRxnBAp4ZPo8RpcAQd2Ry6bZ0Rai/vsEk7WfoLLQ+O5he0v8NrYl0of0 GFwLW+R+HxStND/1AM++OdS9BzMoWC9NuQmyfLiTFFZ2v4E3AaoFh+1NoYxQnful LnTrvs//5FoHwRhmcFZgVirqI= Received: from pek-lpg-core6.wrs.com (unknown []) by gzga-smtp-mtada-g0-0 (Coremail) with SMTP id _____wCntKjfyXlpCRVXIQ--.830S2; Wed, 28 Jan 2026 16:33:37 +0800 (CST) From: Rahul Sharma To: gregkh@linuxfoundation.org, stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Maninder Singh , Shubham Rana , Jeff Layton , Chuck Lever , Rahul Sharma Subject: [PATCH 6.1.y] NFSD: fix race between nfsd registration and exports_proc Date: Wed, 28 Jan 2026 16:33:34 +0800 Message-Id: <20260128083334.2450566-1-black.hawk@163.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _____wCntKjfyXlpCRVXIQ--.830S2 X-Coremail-Antispam: 1Uf129KBjvJXoW3AFWrGF4UCFWrur1xAFy3twb_yoW7Xry8pa n3urW5Kr4vqw1UGa15Jan0yF10qF4kKay8u3s3WaySvwsIg3sFv3WFvF4q9FyDArW8XayD Gw1UKF4F9w1ruaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0zKiiDbUUUUU= X-CM-SenderInfo: 5eoduy4okd4yi6rwjhhfrp/xtbC+QFj-Gl5yeEFrwAA31 Content-Type: text/plain; charset="utf-8" From: Maninder Singh [ Upstream commit f7fb730cac9aafda8b9813b55d04e28a9664d17c ] As of now nfsd calls create_proc_exports_entry() at start of init_nfsd and cleanup by remove_proc_entry() at last of exit_nfsd. Which causes kernel OOPs if there is race between below 2 operations: (i) exportfs -r (ii) mount -t nfsd none /proc/fs/nfsd for 5.4 kernel ARM64: CPU 1: el1_irq+0xbc/0x180 arch_counter_get_cntvct+0x14/0x18 running_clock+0xc/0x18 preempt_count_add+0x88/0x110 prep_new_page+0xb0/0x220 get_page_from_freelist+0x2d8/0x1778 __alloc_pages_nodemask+0x15c/0xef0 __vmalloc_node_range+0x28c/0x478 __vmalloc_node_flags_caller+0x8c/0xb0 kvmalloc_node+0x88/0xe0 nfsd_init_net+0x6c/0x108 [nfsd] ops_init+0x44/0x170 register_pernet_operations+0x114/0x270 register_pernet_subsys+0x34/0x50 init_nfsd+0xa8/0x718 [nfsd] do_one_initcall+0x54/0x2e0 CPU 2 : Unable to handle kernel NULL pointer dereference at virtual address 0000000= 000000010 PC is at : exports_net_open+0x50/0x68 [nfsd] Call trace: exports_net_open+0x50/0x68 [nfsd] exports_proc_open+0x2c/0x38 [nfsd] proc_reg_open+0xb8/0x198 do_dentry_open+0x1c4/0x418 vfs_open+0x38/0x48 path_openat+0x28c/0xf18 do_filp_open+0x70/0xe8 do_sys_open+0x154/0x248 Sometimes it crashes at exports_net_open() and sometimes cache_seq_next_rcu= (). and same is happening on latest 6.14 kernel as well: [ 0.000000] Linux version 6.14.0-rc5-next-20250304-dirty ... [ 285.455918] Unable to handle kernel paging request at virtual address 00= 001f4800001f48 ... [ 285.464902] pc : cache_seq_next_rcu+0x78/0xa4 ... [ 285.469695] Call trace: [ 285.470083] cache_seq_next_rcu+0x78/0xa4 (P) [ 285.470488] seq_read+0xe0/0x11c [ 285.470675] proc_reg_read+0x9c/0xf0 [ 285.470874] vfs_read+0xc4/0x2fc [ 285.471057] ksys_read+0x6c/0xf4 [ 285.471231] __arm64_sys_read+0x1c/0x28 [ 285.471428] invoke_syscall+0x44/0x100 [ 285.471633] el0_svc_common.constprop.0+0x40/0xe0 [ 285.471870] do_el0_svc_compat+0x1c/0x34 [ 285.472073] el0_svc_compat+0x2c/0x80 [ 285.472265] el0t_32_sync_handler+0x90/0x140 [ 285.472473] el0t_32_sync+0x19c/0x1a0 [ 285.472887] Code: f9400885 93407c23 937d7c27 11000421 (f86378a3) [ 285.473422] ---[ end trace 0000000000000000 ]--- It reproduced simply with below script: while [ 1 ] do /exportfs -r done & while [ 1 ] do insmod /nfsd.ko mount -t nfsd none /proc/fs/nfsd umount /proc/fs/nfsd rmmod nfsd done & So exporting interfaces to user space shall be done at last and cleanup at first place. With change there is no Kernel OOPs. Co-developed-by: Shubham Rana Signed-off-by: Shubham Rana Signed-off-by: Maninder Singh Reviewed-by: Jeff Layton Cc: stable@vger.kernel.org Signed-off-by: Chuck Lever [ The context change is due to the commit bd9d6a3efa97 ("NFSD: add rpc_status netlink support") in v6.7 and the proper adoption is done. ] Signed-off-by: Rahul Sharma --- fs/nfsd/nfsctl.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index 07e5b1b23c91..ba2eaf3744ef 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1511,12 +1511,9 @@ static int __init init_nfsd(void) if (retval) goto out_free_pnfs; nfsd_lockd_init(); /* lockd->nfsd callbacks */ - retval =3D create_proc_exports_entry(); - if (retval) - goto out_free_lockd; retval =3D register_pernet_subsys(&nfsd_net_ops); if (retval < 0) - goto out_free_exports; + goto out_free_lockd; retval =3D register_cld_notifier(); if (retval) goto out_free_subsys; @@ -1524,18 +1521,20 @@ static int __init init_nfsd(void) if (retval) goto out_free_cld; retval =3D register_filesystem(&nfsd_fs_type); + if (retval) + goto out_free_nfsd4; + retval =3D create_proc_exports_entry(); if (retval) goto out_free_all; return 0; out_free_all: + unregister_filesystem(&nfsd_fs_type); +out_free_nfsd4: nfsd4_destroy_laundry_wq(); out_free_cld: unregister_cld_notifier(); out_free_subsys: unregister_pernet_subsys(&nfsd_net_ops); -out_free_exports: - remove_proc_entry("fs/nfs/exports", NULL); - remove_proc_entry("fs/nfs", NULL); out_free_lockd: nfsd_lockd_shutdown(); nfsd_drc_slab_free(); @@ -1548,13 +1547,13 @@ static int __init init_nfsd(void) =20 static void __exit exit_nfsd(void) { + remove_proc_entry("fs/nfs/exports", NULL); + remove_proc_entry("fs/nfs", NULL); unregister_filesystem(&nfsd_fs_type); nfsd4_destroy_laundry_wq(); unregister_cld_notifier(); unregister_pernet_subsys(&nfsd_net_ops); nfsd_drc_slab_free(); - remove_proc_entry("fs/nfs/exports", NULL); - remove_proc_entry("fs/nfs", NULL); nfsd_lockd_shutdown(); nfsd4_free_slabs(); nfsd4_exit_pnfs(); --=20 2.34.1