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 85A6724A078; Tue, 21 Jul 2026 20:11:54 +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=1784664717; cv=none; b=r19xDZJoZrmrY3A01+p9rY3O51JPvAW3nOS0dDA0/B/1qGjSlbLZTTldYAKSSGeO8kgS4G50dF1eQZsrVsf9GGqol0rgqSwR3XM5RsZ8xoyKEMlkFDyhyosAMc4ycVxbFLkBnHXQpyVNuTc6oVR9H/lnCqUO3gkVQA0N/vrcmQU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784664717; c=relaxed/simple; bh=qNfevycE0lVrFmQHnWf4+vDta9pms/qCBi/6w9xz4qI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=liu2nlBAI7/lAFEXCUGaC0hJA77vJvgzCQsRibbS+Da6XNe9o62XiJT6C5Vm4l9glRU7ILS9DB4oycvJzcgxno+3/DtWR5QOWdYSVHcvkW1fMF+y1qkFl1tOGi40qtIM9LO+9ggdSf2k0Bf8WewyaoDr3wMKaO/GEupcr8YPW7c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=B7w5m7p3; 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="B7w5m7p3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAFFD1F000E9; Tue, 21 Jul 2026 20:11:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784664714; bh=pPBg/kwTEAPxsF5RA2tO2f/DaBVzZZelL+28f9PTNys=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=B7w5m7p3/LJWp2beDj7YCQ+W90MarTI9LSsx558qD94hWDlY+RqFbSq92J8GunOhf Vsia9HHR72DLvvVjbHtcQZBoWceZLg3r3SCOOp+mqvmjGW8h0nK8xMmBc+fUraZSKm dW+7bP/0eSntbBqMjv1TTxCAD4TFQBk27OMSCZ/M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Denis Arefev , Christoph Hellwig , Jens Axboe , Sasha Levin Subject: [PATCH 6.6 0031/1266] block: Avoid mounting the bdev pseudo-filesystem in userspace Date: Tue, 21 Jul 2026 17:07:48 +0200 Message-ID: <20260721152442.494159496@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152441.786066624@linuxfoundation.org> References: <20260721152441.786066624@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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Denis Arefev [ 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: 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: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- block/bdev.c | 4 ---- 1 file changed, 4 deletions(-) --- 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");