From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 524B824E4C3; Thu, 2 Jul 2026 16:55:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783011329; cv=none; b=F7DvIY1Dg5ko1TuQUqca1AiX7aSa33wgXJYFkUdWGc9gkMGUIo2Xe4TWomoCHnyNO1Wx7IcrBXHLXNfLikLRHYLa85cht02hTspvd6AmijaX6ER3j5944Po3y9AKRta8h2A5PnC9SJy1VR+AtKUhEPAQjy9sYzbIUj1nhPL+Tc4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783011329; c=relaxed/simple; bh=4YJkYxT9l1j9oAxSBj+f7y4OAMxB5QtmG8gp/3mFRfg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kbpdZZoqWyPxs0AZjh97GpJ+sGW4r8yXWfTvzkAYls8Ci+Zc2o3p+G/TpGSbCyYicdsf2XznMwqGHbP1Yx7ERnLDl/aEZnfs6Ut+Og0wXhdxddgGBUfFnntj1v2VVUSW5g9cI6BSiVQxCVxLy6uEtbtEU+2GLC/KiGXS1/oKjDY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=S/nVQcYY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="S/nVQcYY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B89BC1F000E9; Thu, 2 Jul 2026 16:55:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783011328; bh=fZnPjjJOKk/Hg3bYOA089yQMGJqYcc4bqw+VFAxHaVs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=S/nVQcYYr+6B7RscyxI9J6XbsUV3eH2ldVXGB0YkuzWLuphGrXjghDLcpS59DhYsJ zDl2oV8Uu7mBgiOtbrwoQHGD8P2noDtNrdN+wVI4Wl3cHgWwVtTEen0oT2IhHrW6uO wkAzzFQfJFihZOwsXAml+beTNL002q63c2v4atmo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Denis Arefev , Christoph Hellwig , Jens Axboe Subject: [PATCH 6.18 067/108] block: Avoid mounting the bdev pseudo-filesystem in userspace Date: Thu, 2 Jul 2026 18:21:04 +0200 Message-ID: <20260702155113.499036806@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260702155112.110058792@linuxfoundation.org> References: <20260702155112.110058792@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Denis Arefev commit f73aa66dffcb8e61e78f01b56163ec16a15d06d2 upstream. 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: 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 Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260521072857.5078-1-arefev@swemel.ru Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/bdev.c | 5 ----- 1 file changed, 5 deletions(-) --- a/block/bdev.c +++ b/block/bdev.c @@ -438,15 +438,10 @@ 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");