From nobody Sun May 24 21:38:45 2026 Received: from mx.swemel.ru (mx.swemel.ru [95.143.211.150]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4F35E397B02; Thu, 21 May 2026 07:34:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.143.211.150 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779348861; cv=none; b=EtS7zSjjyrTKVuUM0oQkJ43trVvUDFBV6FbFvNsAB5bgt48Dg5Hxwri+3UduTFw09qo40eom1h8u38OWvXmSyFNrKtwW/wca3cw6ILk8zNBbKiyp2mLKGWkoYMtO+pX6ZtigUEsOjKCvCXoIS1F2a9p0pJlgoAUTJbh+rB6TTOQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779348861; c=relaxed/simple; bh=OmnMaX9ik+XuaAJfZZpEW4OaX30cmy0+4VMgXEukpr8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=umh5tAo5i3GUmjiW55biqcNioknlwXHYw46cGXRU06tKgGURejqRmXGVIH7Lj98blWqhJ55Z/67YHkwrPCIZ0su3/YxdHVDOaS8O19smtk4gLQRWAaTayYTAScG5eZg/k3YGph8B6I4Hd7ZnF5Pm+BfXi2pALOuDXK6uF4ZjayM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=swemel.ru; spf=pass smtp.mailfrom=swemel.ru; dkim=pass (1024-bit key) header.d=swemel.ru header.i=@swemel.ru header.b=xIJT839r; arc=none smtp.client-ip=95.143.211.150 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=swemel.ru Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=swemel.ru Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=swemel.ru header.i=@swemel.ru header.b="xIJT839r" From: Denis Arefev DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=swemel.ru; s=mail; t=1779348537; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=pgNeb9y7oioHQCP03azgKcyZm+rXC/BLtQGfBx3gEJs=; b=xIJT839rjwpMDJ9ntjlxhaYBhsAhDZzKnLBjRzKyQ28PcibudhQlwdF59sXgaNXxGA7HtV GmqWrDiv6M06jo+W2egxMt4Sw0MGhupIwv+MV0cjVVDWv6AtMRWP3y0Hxlp9wb1nTkCPw8 +yeRAgbKZgZNIqmtBKinmvQlGPadw80= To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org, stable@vger.kernel.org Subject: [PATCH] block: Avoid mounting the bdev pseudo-filesystem in userspace Date: Thu, 21 May 2026 10:28:56 +0300 Message-ID: <20260521072857.5078-1-arefev@swemel.ru> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 =3D &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=20 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: 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 --- block/bdev.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/block/bdev.c b/block/bdev.c index bb0ffa3bb4df..107ac9eaac7f 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -446,15 +446,10 @@ EXPORT_SYMBOL_GPL(blockdev_superblock); =20 void __init bdev_cache_init(void) { - int err; - bdev_cachep =3D kmem_cache_create("bdev_cache", sizeof(struct bdev_inode), 0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT| SLAB_ACCOUNT|SLAB_PANIC), init_once); - err =3D register_filesystem(&bd_type); - if (err) - panic("Cannot register bdev pseudo-fs"); blockdev_mnt =3D kern_mount(&bd_type); if (IS_ERR(blockdev_mnt)) panic("Cannot create bdev pseudo-fs"); --=20 2.43.0