CVE-2025-37876

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

netfs: Only create /proc/fs/netfs with CONFIGPROCFS

When testing a special config:

CONFIGNETFSSUPPORTS=y CONFIGPROCFS=n

The system crashes with something like:

[ 3.766197] ------------[ cut here ]------------ [ 3.766484] kernel BUG at mm/mempool.c:560! [ 3.766789] Oops: invalid opcode: 0000 [#1] SMP NOPTI [ 3.767123] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W [ 3.767777] Tainted: [W]=WARN [ 3.767968] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), [ 3.768523] RIP: 0010:mempoolallocslab.cold+0x17/0x19 [ 3.768847] Code: 50 fe ff 58 5b 5d 41 5c 41 5d 41 5e 41 5f e9 93 95 13 00 [ 3.769977] RSP: 0018:ffffc90000013998 EFLAGS: 00010286 [ 3.770315] RAX: 000000000000002f RBX: ffff888100ba8640 RCX: 0000000000000000 [ 3.770749] RDX: 0000000000000000 RSI: 0000000000000003 RDI: 00000000ffffffff [ 3.771217] RBP: 0000000000092880 R08: 0000000000000000 R09: ffffc90000013828 [ 3.771664] R10: 0000000000000001 R11: 00000000ffffffea R12: 0000000000092cc0 [ 3.772117] R13: 0000000000000400 R14: ffff8881004b1620 R15: ffffea0004ef7e40 [ 3.772554] FS: 0000000000000000(0000) GS:ffff8881b5f3c000(0000) knlGS:0000000000000000 [ 3.773061] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3.773443] CR2: ffffffff830901b4 CR3: 0000000004296001 CR4: 0000000000770ef0 [ 3.773884] PKRU: 55555554 [ 3.774058] Call Trace: [ 3.774232] <TASK> [ 3.774371] mempoolallocnoprof+0x6a/0x190 [ 3.774649] ? printk+0x57/0x80 [ 3.774862] netfsallocrequest+0x85/0x2ce [ 3.775147] netfsreadahead+0x28/0x170 [ 3.775395] readpages+0x6c/0x350 [ 3.775623] ? srsoaliasreturnthunk+0x5/0xfbef5 [ 3.775928] pagecacheraunbounded+0x1bd/0x2a0 [ 3.776247] filemapgetpages+0x139/0x970 [ 3.776510] ? srsoaliasreturnthunk+0x5/0xfbef5 [ 3.776820] filemapread+0xf9/0x580 [ 3.777054] ? srsoaliasreturnthunk+0x5/0xfbef5 [ 3.777368] ? srsoaliasreturnthunk+0x5/0xfbef5 [ 3.777674] ? findheldlock+0x32/0x90 [ 3.777929] ? netfsstartioread+0x19/0x70 [ 3.778221] ? netfsstartioread+0x19/0x70 [ 3.778489] ? srsoaliasreturnthunk+0x5/0xfbef5 [ 3.778800] ? lockacquired+0x1e6/0x450 [ 3.779054] ? srsoaliasreturnthunk+0x5/0xfbef5 [ 3.779379] netfsbufferedreaditer+0x57/0x80 [ 3.779670] _kernelread+0x158/0x2c0 [ 3.779927] bprmexecve+0x300/0x7a0 [ 3.780185] kernelexecve+0x10c/0x140 [ 3.780423] ? _pfxkernelinit+0x10/0x10 [ 3.780690] kernelinit+0xd5/0x150 [ 3.780910] retfromfork+0x2d/0x50 [ 3.781156] ? _pfxkernelinit+0x10/0x10 [ 3.781414] retfromfork_asm+0x1a/0x30 [ 3.781677] </TASK> [ 3.781823] Modules linked in: [ 3.782065] ---[ end trace 0000000000000000 ]---

This is caused by the following error path in netfs_init():

    if (!proc_mkdir("fs/netfs", NULL))
            goto error_proc;

Fix this by adding ifdef in netfsmain(), so that /proc/fs/netfs is only created with CONFIGPROC_FS.