netdev - Re: kernel panic: corrupted stack end in wb

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d9e4e36d-1e7a-caaf-f96e-b05592405b5f@virtuozzo.com>
Date:   Wed, 20 Mar 2019 12:56:50 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     syzbot <syzbot+ec1b7575afef85a0e5ca@...kaller.appspotmail.com>,
        akpm@...ux-foundation.org, cai@....pw, davem@...emloft.net,
        dvyukov@...gle.com, guro@...com, hannes@...xchg.org, jbacik@...com,
        ktkhai@...tuozzo.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-sctp@...r.kernel.org,
        mgorman@...hsingularity.net, mhocko@...e.com,
        netdev@...r.kernel.org, nhorman@...driver.com, shakeelb@...gle.com,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk,
        vyasevich@...il.com, willy@...radead.org
Cc:     Xin Long <lucien.xin@...il.com>
Subject: Re: kernel panic: corrupted stack end in wb_workfn



On 3/17/19 11:49 PM, syzbot wrote:
> syzbot has bisected this bug to:
> 
> commit c981f254cc82f50f8cb864ce6432097b23195b9c
> Author: Al Viro <viro@...iv.linux.org.uk>
> Date:   Sun Jan 7 18:19:09 2018 +0000
> 
>     sctp: use vmemdup_user() rather than badly open-coding memdup_user()
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137bcecf200000
> start commit:   c981f254 sctp: use vmemdup_user() rather than badly open-c..
> git tree:       upstream
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=10fbcecf200000
> console output: https://syzkaller.appspot.com/x/log.txt?x=177bcecf200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5e7dc790609552d7
> dashboard link: https://syzkaller.appspot.com/bug?extid=ec1b7575afef85a0e5ca
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16a9a84b400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17199bb3400000
> 
> Reported-by: syzbot+ec1b7575afef85a0e5ca@...kaller.appspotmail.com
> Fixes: c981f254 ("sctp: use vmemdup_user() rather than badly open-coding memdup_user()")

>From bisection log:

	testing release v4.17
	testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0
	run #0: crashed: kernel panic: corrupted stack end in wb_workfn
	run #1: crashed: kernel panic: corrupted stack end in worker_thread
	run #2: crashed: kernel panic: Out of memory and no killable processes...
	run #3: crashed: kernel panic: corrupted stack end in wb_workfn
	run #4: crashed: kernel panic: corrupted stack end in wb_workfn
	run #5: crashed: kernel panic: corrupted stack end in wb_workfn
	run #6: crashed: kernel panic: corrupted stack end in wb_workfn
	run #7: crashed: kernel panic: corrupted stack end in wb_workfn
	run #8: crashed: kernel panic: Out of memory and no killable processes...
	run #9: crashed: kernel panic: corrupted stack end in wb_workfn
	testing release v4.16
	testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda with gcc (GCC) 8.1.0
	run #0: OK
	run #1: OK
	run #2: OK
	run #3: OK
	run #4: OK
	run #5: crashed: kernel panic: Out of memory and no killable processes...
	run #6: OK
	run #7: crashed: kernel panic: Out of memory and no killable processes...
	run #8: OK
	run #9: OK
	testing release v4.15
	testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff with gcc (GCC) 8.1.0
	all runs: OK
	# git bisect start v4.16 v4.15

Why bisect started between 4.16 4.15 instead of 4.17 4.16?


	testing commit c14376de3a1befa70d9811ca2872d47367b48767 with gcc (GCC) 8.1.0
	run #0: crashed: kernel panic: Out of memory and no killable processes...
	run #1: crashed: kernel panic: Out of memory and no killable processes...
	run #2: crashed: kernel panic: Out of memory and no killable processes...
	run #3: crashed: kernel panic: Out of memory and no killable processes...
	run #4: OK
	run #5: OK
	run #6: crashed: WARNING: ODEBUG bug in netdev_freemem
	run #7: crashed: no output from test machine
	run #8: OK
	run #9: OK
	# git bisect bad c14376de3a1befa70d9811ca2872d47367b48767

Why c14376de3a1befa70d9811ca2872d47367b48767 is bad? There was no stack corruption.
It looks like the syzbot were bisecting a different bug - "kernel panic: Out of memory and no killable processes..."
And bisection for that bug seems to be correct. kvmalloc() in vmemdup_user() may eat up all memory unlike kmalloc which is limited by KMALLOC_MAX_SIZE (4MB usually).