[lvc-project] [PATCH] block: Avoid mounting the bdev pseudo-filesystem in userspace

[Fedor Pchelkin]

On Thu, 21. May 10:28, Denis Arefev wrote:
> 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.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Link: https://lore.kernel.org/all/20131010004732.GJ13318@ZenIV.linux.org.uk/T/#
> Cc: stable at vger.kernel.org
> Signed-off-by: Denis Arefev <arefev at swemel.ru>

Для веток 5.10 и 6.1 понадобится адаптированная версия патча в
lvc-patches.