CVE-2025-38232 — NFSD: fix race between nfsd registration and exports_proc

Affected: Linux, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP, Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

In the Linux kernel, the following vulnerability has been resolved:

NFSD: fix race between nfsd registration and exports_proc

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 req…

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CVE-2025-38232 — NFSD: fix race between nfsd registration and exports_proc