From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF650C433FE for ; Sat, 26 Feb 2022 09:43:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230456AbiBZJo0 (ORCPT ); Sat, 26 Feb 2022 04:44:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35684 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229819AbiBZJoZ (ORCPT ); Sat, 26 Feb 2022 04:44:25 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0540126E6; Sat, 26 Feb 2022 01:43:49 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 331BDCE04AE; Sat, 26 Feb 2022 09:43:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 14EFFC340E8; Sat, 26 Feb 2022 09:43:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1645868626; bh=JTaGggqJo40LTAh1rqoyqhHAX2dNKs4MvAGcL3I/2YU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=u7BR+RpQbRGhCwzfThQMyQYRgeSFA3JtinFe9HxlpY5H6w0ahWTgZ0bJ5/7ORsbtq nyHNwJQ8N0/2S4jGJX9KRzLgYEfw9K8+phb5KyWe702xvAZy9I/pk/6wm5V5W8vbxj k1MJip36ObubPTdCazR4Ufr/T/HOp0aPcCtvizEI= Date: Sat, 26 Feb 2022 10:43:44 +0100 From: Greg KH To: Yu Kuai Cc: axboe@kernel.dk, rostedt@goodmis.org, mingo@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com Subject: Re: [PATCH] blktrace: Revert "blktrace: remove debugfs file dentries from struct blk_trace" Message-ID: References: <20220226095343.1121256-1-yukuai3@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220226095343.1121256-1-yukuai3@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 26, 2022 at 05:53:43PM +0800, Yu Kuai wrote: > This reverts commit c0ea57608b691d6cde8aff23e11f9858a86b5918. > > When tracing the whole disk, 'dropped' and 'msg' will be created > under 'q->debugfs_dir' and 'bt->dir' is NULL, thus blk_trace_free() > won't remove those files. What's worse, the following UAF can be > triggered because of stale 'dropped' and 'msg': Only root has access to these files, right? > > ================================================================== > BUG: KASAN: use-after-free in blk_dropped_read+0x89/0x100 > Read of size 4 at addr ffff88816912f3d8 by task blktrace/1188 > > CPU: 27 PID: 1188 Comm: blktrace Not tainted 5.17.0-rc4-next-20220217+ #469 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-4 > Call Trace: > > dump_stack_lvl+0x34/0x44 > print_address_description.constprop.0.cold+0xab/0x381 > ? blk_dropped_read+0x89/0x100 > ? blk_dropped_read+0x89/0x100 > kasan_report.cold+0x83/0xdf > ? blk_dropped_read+0x89/0x100 > kasan_check_range+0x140/0x1b0 > blk_dropped_read+0x89/0x100 > ? blk_create_buf_file_callback+0x20/0x20 > ? kmem_cache_free+0xa1/0x500 > ? do_sys_openat2+0x258/0x460 > full_proxy_read+0x8f/0xc0 > vfs_read+0xc6/0x260 > ksys_read+0xb9/0x150 > ? vfs_write+0x3d0/0x3d0 > ? fpregs_assert_state_consistent+0x55/0x60 > ? exit_to_user_mode_prepare+0x39/0x1e0 > do_syscall_64+0x35/0x80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x7fbc080d92fd > Code: ce 20 00 00 75 10 b8 00 00 00 00 0f 05 48 3d 01 f0 ff ff 73 31 c3 48 83 1 > RSP: 002b:00007fbb95ff9cb0 EFLAGS: 00000293 ORIG_RAX: 0000000000000000 > RAX: ffffffffffffffda RBX: 00007fbb95ff9dc0 RCX: 00007fbc080d92fd > RDX: 0000000000000100 RSI: 00007fbb95ff9cc0 RDI: 0000000000000045 > RBP: 0000000000000045 R08: 0000000000406299 R09: 00000000fffffffd > R10: 000000000153afa0 R11: 0000000000000293 R12: 00007fbb780008c0 > R13: 00007fbb78000938 R14: 0000000000608b30 R15: 00007fbb780029c8 > > > Allocated by task 1050: > kasan_save_stack+0x1e/0x40 > __kasan_kmalloc+0x81/0xa0 > do_blk_trace_setup+0xcb/0x410 > __blk_trace_setup+0xac/0x130 > blk_trace_ioctl+0xe9/0x1c0 > blkdev_ioctl+0xf1/0x390 > __x64_sys_ioctl+0xa5/0xe0 > do_syscall_64+0x35/0x80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > Freed by task 1050: > kasan_save_stack+0x1e/0x40 > kasan_set_track+0x21/0x30 > kasan_set_free_info+0x20/0x30 > __kasan_slab_free+0x103/0x180 > kfree+0x9a/0x4c0 > __blk_trace_remove+0x53/0x70 > blk_trace_ioctl+0x199/0x1c0 > blkdev_common_ioctl+0x5e9/0xb30 > blkdev_ioctl+0x1a5/0x390 > __x64_sys_ioctl+0xa5/0xe0 > do_syscall_64+0x35/0x80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > The buggy address belongs to the object at ffff88816912f380 > which belongs to the cache kmalloc-96 of size 96 > The buggy address is located 88 bytes inside of > 96-byte region [ffff88816912f380, ffff88816912f3e0) > The buggy address belongs to the page: > page:000000009a1b4e7c refcount:1 mapcount:0 mapping:0000000000000000 index:0x0f > flags: 0x17ffffc0000200(slab|node=0|zone=2|lastcpupid=0x1fffff) > raw: 0017ffffc0000200 ffffea00044f1100 dead000000000002 ffff88810004c780 > raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff88816912f280: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > ffff88816912f300: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > >ffff88816912f380: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > ^ > ffff88816912f400: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > ffff88816912f480: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > ================================================================== > > Fixes: c0ea57608b69 ("blktrace: remove debugfs file dentries from struct blk_trace") > Signed-off-by: Yu Kuai > --- > include/linux/blktrace_api.h | 2 ++ > kernel/trace/blktrace.c | 8 ++++++-- > 2 files changed, 8 insertions(+), 2 deletions(-) > > diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h > index 22501a293fa5..f288d229727c 100644 > --- a/include/linux/blktrace_api.h > +++ b/include/linux/blktrace_api.h > @@ -23,6 +23,8 @@ struct blk_trace { > u32 pid; > u32 dev; > struct dentry *dir; > + struct dentry *dropped_file; > + struct dentry *msg_file; No need to save these dentries. Just look them up when you want to remove the files. > struct list_head running_list; > atomic_t dropped; > }; > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > index 19514edc44f7..13152a17fdb3 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -312,6 +312,8 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes, > > static void blk_trace_free(struct blk_trace *bt) > { > + debugfs_remove(bt->msg_file); > + debugfs_remove(bt->dropped_file); > relay_close(bt->rchan); > debugfs_remove(bt->dir); Why not just move this line up above relay_close()? Then you the whole directory is properly removed, along with the files in it. So this can just be a 1 line change :) thanks, greg k-h