From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EA804201022; Thu, 6 Mar 2025 12:08:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741262889; cv=none; b=JJ+eCO91/u9s61tQac6baKQ4HMvCqyIQL0xGJa6aiZC9mDhdwRdQJRBTrl6770iraDfmPjO/EAvU0pbo60Q3daSiAagLoGnZZqXJ6uXS+4JKM/cEjX+BO1Ye5EtcHqjWhaEbd3YZCsXidGaCiwR7ciWbtOoudJPDHmIZAJUvEu8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741262889; c=relaxed/simple; bh=lobxsGXQH9XsJhkYc/IBFLm9ndnD9CqNtlDGa7DUloc=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=rUj1Y2T0Iys92+9oWAosZE8zjB+MhXHaXHBX5wZPWYEziNvfJPlw/PVkKsSiBmMyLfo1WOdcYCF5UGuZMa9TDn7drzS67DTG2ubVUhuOD4RhEWik8sB8bOumZgy/dof9JZpRAP1chYSimuNUvEsscZlFfLoDJIMdG89Xk3B2LFI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VvV2RCBU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VvV2RCBU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68FEBC4CEE0; Thu, 6 Mar 2025 12:08:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741262888; bh=lobxsGXQH9XsJhkYc/IBFLm9ndnD9CqNtlDGa7DUloc=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=VvV2RCBUgyAKtcOzcBcQ5VFPIpjskYij2cFQ5yWi0x5ZLrpF+Mnxp7N2qmEYa2Vk1 xSohKONmubqMjrN8NxTJmqY/D/G0gK0WRcZhDqNuB/x7MWNUWE1Qy9Gig6eE5tnvOs K0hTnpdpXV7ZKmN0ZfltaB+QpGBxLtQhw3stmLEu6ZWWZQJmNKhxOSbi4g2KaHJe9D NlWKTc6UvDfSWTL4tHTw06gv1rgabQgopMuUgiuQhoM7DKjyADNg7NZcaXZXrYzBC4 PlPfxBkoRh0LIFk1S1LnSsUFh1tkiI9oRlqY8PWuni8zCJNjNcJnGmEW2ZEj02pcnQ NTf2WPVjgPQLA== Message-ID: Subject: Re: [PATCH 2/2] NFSD: fix race between nfsd registration and exports_proc From: Jeff Layton To: Maninder Singh , chuck.lever@oracle.com, neilb@suse.de, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, lorenzo@kernel.org Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, chungki0201.woo@samsung.com, Shubham Rana Date: Thu, 06 Mar 2025 07:08:06 -0500 In-Reply-To: <20250306092007.1419237-2-maninder1.s@samsung.com> References: <20250306092007.1419237-1-maninder1.s@samsung.com> <20250306092007.1419237-2-maninder1.s@samsung.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv 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linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2025-03-06 at 14:50 +0530, Maninder Singh wrote: > 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. >=20 > Which causes kernel OOPs if there is race between below 2 operations: > (i) exportfs -r > (ii) mount -t nfsd none /proc/fs/nfsd >=20 > for 5.4 kernel ARM64: >=20 > 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 >=20 > CPU 2 : > Unable to handle kernel NULL pointer dereference at virtual address 00000= 00000000010 >=20 > PC is at : exports_net_open+0x50/0x68 [nfsd] >=20 > 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 >=20 > Sometimes it crashes at exports_net_open() and sometimes cache_seq_next_r= cu(). >=20 > and same is happening on latest 6.14 kernel as well: >=20 > [ 0.000000] Linux version 6.14.0-rc5-next-20250304-dirty > ... > [ 285.455918] Unable to handle kernel paging request at virtual address = 00001f4800001f48 > ... > [ 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 ]--- >=20 > It reproduced simply with below script: > while [ 1 ] > do > /exportfs -r > done & >=20 > while [ 1 ] > do > insmod /nfsd.ko > mount -t nfsd none /proc/fs/nfsd > umount /proc/fs/nfsd > rmmod nfsd > done & >=20 > So exporting interfaces to user space shall be done at last and > cleanup at first place. >=20 > With change there is no Kernel OOPs. >=20 > Co-developed-by: Shubham Rana > Signed-off-by: Shubham Rana > Signed-off-by: Maninder Singh > --- > fs/nfsd/nfsctl.c | 17 ++++++++--------- > 1 file changed, 8 insertions(+), 9 deletions(-) >=20 > diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c > index d773481bcf10..f9763ced743d 100644 > --- a/fs/nfsd/nfsctl.c > +++ b/fs/nfsd/nfsctl.c > @@ -2291,12 +2291,9 @@ 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; > @@ -2307,12 +2304,17 @@ static int __init init_nfsd(void) > if (retval) > goto out_free_nfsd4; > retval =3D genl_register_family(&nfsd_nl_family); > + if (retval) > + goto out_free_filesystem; > + retval =3D create_proc_exports_entry(); > if (retval) > goto out_free_all; > nfsd_localio_ops_init(); > =20 > return 0; > out_free_all: > + genl_unregister_family(&nfsd_nl_family); > +out_free_filesystem: > unregister_filesystem(&nfsd_fs_type); > out_free_nfsd4: > nfsd4_destroy_laundry_wq(); > @@ -2320,9 +2322,6 @@ static int __init init_nfsd(void) > 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(); > @@ -2335,14 +2334,14 @@ 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); > genl_unregister_family(&nfsd_nl_family); > 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(); To make sure I understand, the race is that sometimes the exports interface gets created before the net namespace is set up, and then that causes GPFs when exports_net_open tries to access the nfsd_net? Thanks, --=20 Jeff Layton