netdev - Re: KASAN: invalid-free in tcf_exts

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Date:   Tue, 10 Mar 2020 13:36:02 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        syzbot <syzbot+dcc34d54d68ef7d2d53d@...kaller.appspotmail.com>
Cc:     David Miller <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jakub Kicinski <kuba@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: invalid-free in tcf_exts_destroy



On 3/10/20 11:33 AM, Cong Wang wrote:
> On Sun, Mar 8, 2020 at 12:35 PM syzbot
> <syzbot+dcc34d54d68ef7d2d53d@...kaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    c2003765 Merge tag 'io_uring-5.6-2020-03-07' of git://git...
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=10cd2ae3e00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=4527d1e2fb19fd5c
>> dashboard link: https://syzkaller.appspot.com/bug?extid=dcc34d54d68ef7d2d53d
>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>> userspace arch: i386
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1561b01de00000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15aad2f9e00000
>>
>> The bug was bisected to:
>>
>> commit 599be01ee567b61f4471ee8078870847d0a11e8e
>> Author: Cong Wang <xiyou.wangcong@...il.com>
>> Date:   Mon Feb 3 05:14:35 2020 +0000
>>
>>     net_sched: fix an OOB access in cls_tcindex
>>
>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10a275fde00000
>> final crash:    https://syzkaller.appspot.com/x/report.txt?x=12a275fde00000
>> console output: https://syzkaller.appspot.com/x/log.txt?x=14a275fde00000
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+dcc34d54d68ef7d2d53d@...kaller.appspotmail.com
>> Fixes: 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex")
>>
>> IPVS: ftp: loaded support on port[0] = 21
>> ==================================================================
>> BUG: KASAN: double-free or invalid-free in tcf_exts_destroy+0x62/0xc0 net/sched/cls_api.c:3002
>>
>> CPU: 1 PID: 9507 Comm: syz-executor467 Not tainted 5.6.0-rc4-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:77 [inline]
>>  dump_stack+0x188/0x20d lib/dump_stack.c:118
>>  print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:374
>>  kasan_report_invalid_free+0x61/0xa0 mm/kasan/report.c:468
>>  __kasan_slab_free+0x129/0x140 mm/kasan/common.c:455
>>  __cache_free mm/slab.c:3426 [inline]
>>  kfree+0x109/0x2b0 mm/slab.c:3757
>>  tcf_exts_destroy+0x62/0xc0 net/sched/cls_api.c:3002
>>  tcf_exts_change+0xf4/0x150 net/sched/cls_api.c:3059
>>  tcindex_set_parms+0xed8/0x1a00 net/sched/cls_tcindex.c:456
> 
> Looks like a consequence of "slab-out-of-bounds Write in tcindex_set_parms".
> 
> Thanks.
> 

I have a dozen more syzbot reports involving net/sched code, do you want
me to release them right now ?