6.15-stable review patch. If anyone has any objections, please let me know.
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From: Maninder Singh maninder1.s@samsung.com
commit f7fb730cac9aafda8b9813b55d04e28a9664d17c upstream.
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 0000000000000010
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 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 ]---
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 s9.rana@samsung.com Signed-off-by: Shubham Rana s9.rana@samsung.com Signed-off-by: Maninder Singh maninder1.s@samsung.com Reviewed-by: Jeff Layton jlayton@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/nfsd/nfsctl.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-)
--- 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 = create_proc_exports_entry(); - if (retval) - goto out_free_lockd; retval = register_pernet_subsys(&nfsd_net_ops); if (retval < 0) - goto out_free_exports; + goto out_free_lockd; retval = register_cld_notifier(); if (retval) goto out_free_subsys; @@ -2308,11 +2305,16 @@ static int __init init_nfsd(void) goto out_free_nfsd4; retval = genl_register_family(&nfsd_nl_family); if (retval) + goto out_free_filesystem; + retval = create_proc_exports_entry(); + if (retval) goto out_free_all; nfsd_localio_ops_init();
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 @@ 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(); @@ -2335,14 +2334,14 @@ out_free_slabs:
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();