Linux kernel: Bdev pseudo-fs mount NULL deref (DoS)
CVE-2026-63810 Published on July 19, 2026
block: Avoid mounting the bdev pseudo-filesystem in userspace
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.
Products Associated with CVE-2026-63810
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Affected Versions
Linux:- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 3d3fcf23993bb756de2f912ab631cfdcc4746554 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 99cde0a7b1e98fd3970aabef1300918e91698dd5 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 1a02a5028bd6dead1f8503854ef3168d651cd417 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 197971e6ffc0a6356b2ba2b22beb42bc0f7e412d is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 3804e6de30ae7b053d53341d9d6944356cf23b40 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 717f721eb67d2dacd3ed5f7495aef2f442e84ce4 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below f73aa66dffcb8e61e78f01b56163ec16a15d06d2 is affected.
- Version 2.6.12 is affected.
- Before 2.6.12 is unaffected.
- Version 5.15.212, <= 5.15.* is unaffected.
- Version 6.1.178, <= 6.1.* is unaffected.
- Version 6.6.145, <= 6.6.* is unaffected.
- Version 6.12.95, <= 6.12.* is unaffected.
- Version 6.18.38, <= 6.18.* is unaffected.
- Version 7.1.3, <= 7.1.* is unaffected.
- Version 7.2, <= * is unaffected.