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Maninder Singh 2029ca75cd NFSD: fix race between nfsd registration and exports_proc 
commit f7fb730cac 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>
History 2025-06-27 11:11:15 +01:00
arch s390/pci: Serialize device addition and removal 2025-06-27 11:11:14 +01:00
block block: don't use submit_bio_noacct_nocheck in blk_zone_wplug_bio_work 2025-06-19 15:32:33 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Redo lookup on EEXIST 2025-06-19 15:31:30 +02:00
Documentation regulator: dt-bindings: mt6357: Drop fixed compatible requirement 2025-06-19 15:32:37 +02:00
drivers wifi: ath11k: fix ring-buffer corruption 2025-06-27 11:11:15 +01:00
fs NFSD: fix race between nfsd registration and exports_proc 2025-06-27 11:11:15 +01:00
include overflow: Introduce __DEFINE_FLEX for having no initializer 2025-06-19 15:32:37 +02:00
init rust: clean Rust 1.88.0's unnecessary_transmutes lint 2025-05-18 08:24:51 +02:00
io_uring io_uring/kbuf: account ring io_buffer_list memory 2025-06-27 11:11:14 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel ring-buffer: Move cpus_read_lock() outside of buffer->mutex 2025-06-19 15:32:36 +02:00
lib iov_iter: use iov_offset for length calculation in iov_iter_aligned_bvec 2025-06-19 15:32:21 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm page_pool: Move pp_magic check into helper functions 2025-06-19 15:31:42 +02:00
net calipso: unlock rcu before returning -EAFNOSUPPORT 2025-06-19 15:32:37 +02:00
rust rust: alloc: add missing invariant in Vec::set_len() 2025-06-19 15:32:09 +02:00
samples samples/bpf: Fix compilation failure for samples/bpf on LoongArch Fedora 2025-05-29 11:02:01 +02:00
scripts randstruct: gcc-plugin: Fix attribute addition 2025-06-19 15:32:04 +02:00
security smack: Revert "smackfs: Added check catlen" 2025-05-29 11:02:48 +02:00
sound ASoC: amd: sof_amd_sdw: Fix unlikely uninitialized variable use in create_sdw_dailinks() 2025-06-27 11:11:13 +01:00
tools tools/resolve_btfids: Fix build when cross compiling kernel with clang. 2025-06-19 15:32:33 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Add member to struct kvm_gfn_range to indicate private/shared 2025-05-22 14:29:36 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-18 08:24:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.34 2025-06-19 15:32:38 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.