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 C0B462DEA98; Thu, 2 Jul 2026 17:00:30 +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=1783011631; cv=none; b=Kdt/SsxmlTmtngWU5RWxeTxq4xKHDGl+Man58T1qNwHmCYvpgPjcVNQ8Vv30StyPhAxxI4mwORhjH7frzXD/00bfRFaG/U5NAvMuwm7DWRdPshLwKseFgtu74NCyXh+CAHuh4aOsBWjmhb/GGRko8L2V0kSyqOybX0xurZ4O27s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783011631; c=relaxed/simple; bh=30NZlt7MUBcKs5AD+9ek9OeFg12eCKs/YPwZIdvQPZA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZNPOiWY/2gvMghFgQABqOHkrBNROOiu1TZTRByumZP1Lu1GI5PnZLH61ktqh8V/tK9sOi4Hda9HHCtSZJ+st5zxwk143R9jY5zc7yF9xpsucGRy89SzucbsDwPnKYZEirc3cdiCus1J6gon0FICzGMiCrw6s1Ti/TZAyz6Cuh7w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=x/xOWETo; 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="x/xOWETo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07D741F00A3D; Thu, 2 Jul 2026 17:00:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783011630; bh=HpKIRq5k2dY0FJsOVkFylLtJY0Bc0P9s98niATktNzs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=x/xOWETorOw429k9vqHy6lszb4OS23VQHuz5covLtuTNenzlwXHW2ZDOWOEl6Zc84 1HT1ahtknPjo6KKH5l2oKoOF2LgQRqOXPPcpHo5ycmGPKwVrjjVdhQZBkk78aWLlJn eNcv/MoMEVgghRVVfPpHhTdANrM1/bkJ+KvLPQm8= 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 7.1 073/120] block: Avoid mounting the bdev pseudo-filesystem in userspace Date: Thu, 2 Jul 2026 18:21:09 +0200 Message-ID: <20260702155114.468451877@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260702155112.964534952@linuxfoundation.org> References: <20260702155112.964534952@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 7.1-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 @@ -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");