Re: KASAN: invalid-free in tcf_exts_destroy

[Cong Wang]

On Tue, Mar 10, 2020 at 1:36 PM Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
>
>
>
> On 3/10/20 11:33 AM, Cong Wang wrote:
> > On Sun, Mar 8, 2020 at 12:35 PM syzbot
> > <syzbot+dcc34d54d68ef7d2d53d@xxxxxxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxx>
> >> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> >> 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 ?

I have no problem with this, at least I can close them as dup etc.. Please
go ahead.

Thanks.