linux-kernel - RE: [syzbot] kernel panic: corrupted stack end in rtnl

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Date:   Mon, 14 Mar 2022 10:43:58 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Dmitry Vyukov' <dvyukov@...gle.com>,
        syzbot <syzbot+0600986d88e2d4d7ebb8@...kaller.appspotmail.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "dsahern@...nel.org" <dsahern@...nel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        "yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: RE: [syzbot] kernel panic: corrupted stack end in rtnl_newlink

From: Dmitry Vyukov
> Sent: 14 March 2022 09:09
> 
> On Mon, 14 Mar 2022 at 09:22, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> >
> > On Mon, 14 Mar 2022 at 09:17, syzbot
> > <syzbot+0600986d88e2d4d7ebb8@...kaller.appspotmail.com> wrote:
> > >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    0966d385830d riscv: Fix auipc+jalr relocation range checks
> > > git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git fixes
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=17fe80c5700000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=6295d67591064921
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=0600986d88e2d4d7ebb8
> > > compiler:       riscv64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for
> Debian) 2.35.2
> > > userspace arch: riscv64
> >
> > +linux-riscv
> >
> > Riscv needs to increase stack size under KASAN.
> > I will send a patch.

With vmalloc()ed stacks is it possible to allocate an extra page
of KVA that isn't backed by memory as a 'guard page' so that
stack overflow faults immediately?

Probably worth enforcing for KASAN builds where the compilers
have a nasty habit of using lot more stack space that might
be expected.

	David

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