* FAILED: patch "[PATCH] block: Avoid mounting the bdev pseudo-filesystem in userspace" failed to apply to 6.6-stable tree
@ 2026-07-02 13:12 gregkh
2026-07-04 11:53 ` [PATCH 6.6.y] block: Avoid mounting the bdev pseudo-filesystem in userspace Sasha Levin
0 siblings, 1 reply; 2+ messages in thread
From: gregkh @ 2026-07-02 13:12 UTC (permalink / raw)
To: arefev, axboe, hch; +Cc: stable
The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x f73aa66dffcb8e61e78f01b56163ec16a15d06d2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026070221-delegate-colonize-15f6@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f73aa66dffcb8e61e78f01b56163ec16a15d06d2 Mon Sep 17 00:00:00 2001
From: Denis Arefev <arefev@swemel.ru>
Date: Thu, 21 May 2026 10:28:56 +0300
Subject: [PATCH] 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.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Link: https://lore.kernel.org/all/20131010004732.GJ13318@ZenIV.linux.org.uk/T/#
Cc: stable@vger.kernel.org
Signed-off-by: Denis Arefev <arefev@swemel.ru>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260521072857.5078-1-arefev@swemel.ru
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/bdev.c b/block/bdev.c
index e44a73903201..85ce57bd2ae4 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -446,15 +446,10 @@ EXPORT_SYMBOL_GPL(blockdev_superblock);
void __init bdev_cache_init(void)
{
- int err;
-
bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
SLAB_ACCOUNT|SLAB_PANIC),
init_once);
- err = register_filesystem(&bd_type);
- if (err)
- panic("Cannot register bdev pseudo-fs");
blockdev_mnt = kern_mount(&bd_type);
if (IS_ERR(blockdev_mnt))
panic("Cannot create bdev pseudo-fs");
^ permalink raw reply related [flat|nested] 2+ messages in thread* [PATCH 6.6.y] block: Avoid mounting the bdev pseudo-filesystem in userspace
2026-07-02 13:12 FAILED: patch "[PATCH] block: Avoid mounting the bdev pseudo-filesystem in userspace" failed to apply to 6.6-stable tree gregkh
@ 2026-07-04 11:53 ` Sasha Levin
0 siblings, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2026-07-04 11:53 UTC (permalink / raw)
To: stable; +Cc: Denis Arefev, Christoph Hellwig, Jens Axboe, Sasha Levin
From: Denis Arefev <arefev@swemel.ru>
[ Upstream commit f73aa66dffcb8e61e78f01b56163ec16a15d06d2 ]
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@vger.kernel.org
Signed-off-by: Denis Arefev <arefev@swemel.ru>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260521072857.5078-1-arefev@swemel.ru
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/bdev.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/block/bdev.c b/block/bdev.c
index a8357b72a27b86..598f94827b941f 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -383,16 +383,12 @@ EXPORT_SYMBOL_GPL(blockdev_superblock);
void __init bdev_cache_init(void)
{
- int err;
static struct vfsmount *bd_mnt;
bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD|SLAB_ACCOUNT|SLAB_PANIC),
init_once);
- err = register_filesystem(&bd_type);
- if (err)
- panic("Cannot register bdev pseudo-fs");
bd_mnt = kern_mount(&bd_type);
if (IS_ERR(bd_mnt))
panic("Cannot create bdev pseudo-fs");
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
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2026-07-02 13:12 FAILED: patch "[PATCH] block: Avoid mounting the bdev pseudo-filesystem in userspace" failed to apply to 6.6-stable tree gregkh
2026-07-04 11:53 ` [PATCH 6.6.y] block: Avoid mounting the bdev pseudo-filesystem in userspace Sasha Levin
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