From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@lst.de>, Eric Biggers <ebiggers@kernel.org>
Cc: "syzbot+51177e4144d764827c45@syzkaller.appspotmail.com"
<syzbot+51177e4144d764827c45@syzkaller.appspotmail.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"syzkaller-bugs@googlegroups.com"
<syzkaller-bugs@googlegroups.com>,
"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>
Subject: RE: WARNING in __kernel_read (2)
Date: Tue, 29 Sep 2020 08:06:32 +0000 [thread overview]
Message-ID: <e81e2721e8ce4612b0fc6098d311d378@AcuMS.aculab.com> (raw)
In-Reply-To: <20200929065601.GA2095@lst.de>
From: Christoph Hellwig
> Sent: 29 September 2020 07:56
>
> On Mon, Sep 28, 2020 at 11:46:48PM -0700, Eric Biggers wrote:
> > > Linus asked for it. What is the call chain that we hit it with?
> >
> > Call Trace:
> > kernel_read+0x52/0x70 fs/read_write.c:471
> > kernel_read_file fs/exec.c:989 [inline]
> > kernel_read_file+0x2e5/0x620 fs/exec.c:952
> > kernel_read_file_from_fd+0x56/0xa0 fs/exec.c:1076
> > __do_sys_finit_module+0xe6/0x190 kernel/module.c:4066
> > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
> > entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >
> > See the email from syzbot for the full details:
> > https://lkml.kernel.org/linux-fsdevel/000000000000da992305b02e9a51@google.com
>
> Passing a fs without read permissions definitively looks bogus for
> the finit_module syscall. So I think all we need is an extra check
> to validate the fd.
The sysbot test looked like it didn't even have a regular file.
I thought I saw a test for that - but it might be in a different path.
You do need to ensure that 'exec' doesn't need read access.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
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next prev parent reply other threads:[~2020-09-29 8:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-26 2:58 syzbot
2020-09-26 11:15 ` David Laight
2020-09-26 13:17 ` David Laight
2020-09-28 22:14 ` Eric Biggers
2020-09-29 6:38 ` Christoph Hellwig
2020-09-29 6:46 ` Eric Biggers
2020-09-29 6:56 ` Christoph Hellwig
2020-09-29 8:06 ` David Laight [this message]
2020-09-29 8:21 ` Dmitry Vyukov
2020-09-29 10:21 ` Christoph Hellwig
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