CVE-2026-63810

block: Avoid mounting the bdev pseudo-filesystem in userspace

State: Published
Severity: Not scored
Published: Jul 19, 2026
Updated: Oct 15, 2026
Reserved: Jul 19, 2026

Description

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

block: Avoid mounting the bdev pseudo-filesystem in userspace

The bdev pseudo-filesystem is an internal kernel filesystem with which userspace should not interfere. Unregister it so that userspace cannot even attempt to mount it.

This fixes a bug [1] that occurs when attempting to access files, because the system call move_mount() uses pointers declared in the inode_operations structure, which for the bdev pseudo-filesystem are always equal to 0. `inode->i_op = &empty_iops;`

[1]

BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0010) - not-present page PGD 23380067 P4D 23380067 PUD 23381067 PMD 0 Oops: 0010 [#1] PREEMPT SMP KASAN NOPTI CPU: 2 PID: 17125 Comm: syz-executor.0 Not tainted 6.1.155-syzkaller-00350-g84221fde2681 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:0x0

Call Trace: <TASK> lookup_open.isra.0+0x700/0x1180 fs/namei.c:3460 open_last_lookups fs/namei.c:3550 [inline] path_openat+0x953/0x2700 fs/namei.c:3780 do_filp_open+0x1c5/0x410 fs/namei.c:3810 do_sys_openat2+0x171/0x4d0 fs/open.c:1318 do_sys_open fs/open.c:1334 [inline] __do_sys_openat fs/open.c:1350 [inline] __se_sys_openat fs/open.c:1345 [inline] __x64_sys_openat+0x13c/0x1f0 fs/open.c:1345 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 3d3fcf23993bb756de2f912ab631cfdcc4746554Affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 99cde0a7b1e98fd3970aabef1300918e91698dd5Affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 1a02a5028bd6dead1f8503854ef3168d651cd417Affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 197971e6ffc0a6356b2ba2b22beb42bc0f7e412dAffected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 3804e6de30ae7b053d53341d9d6944356cf23b40Affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 717f721eb67d2dacd3ed5f7495aef2f442e84ce4Affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before f73aa66dffcb8e61e78f01b56163ec16a15d06d2Affected
LinuxLinux	2.6.12Affected before 2.6.12Not affected 5.15.212 through 5.15.Not affected 6.1.178 through 6.1.Not affected 6.6.145 through 6.6.Not affected 6.12.95 through 6.12.Not affected 6.18.38 through 6.18.Not affected 7.1.3 through 7.1.Not affected 7.2 and laterNot affected

Product

Versions

LinuxLinux

1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 3d3fcf23993bb756de2f912ab631cfdcc4746554Affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 99cde0a7b1e98fd3970aabef1300918e91698dd5Affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 1a02a5028bd6dead1f8503854ef3168d651cd417Affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 197971e6ffc0a6356b2ba2b22beb42bc0f7e412dAffected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 3804e6de30ae7b053d53341d9d6944356cf23b40Affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 717f721eb67d2dacd3ed5f7495aef2f442e84ce4Affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before f73aa66dffcb8e61e78f01b56163ec16a15d06d2Affected

LinuxLinux

2.6.12Affected
before 2.6.12Not affected
5.15.212 through 5.15.*Not affected
6.1.178 through 6.1.*Not affected
6.6.145 through 6.6.*Not affected
6.12.95 through 6.12.*Not affected
6.18.38 through 6.18.*Not affected
7.1.3 through 7.1.*Not affected
7.2 and laterNot affected

References

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