linux-kernel - RE: WARNING in __kernel

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Date:   Sat, 26 Sep 2020 13:17:04 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     David Laight <David.Laight@...LAB.COM>,
        'syzbot' <syzbot+51177e4144d764827c45@...kaller.appspotmail.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>
Subject: RE: WARNING in __kernel_read (2)

From: David Laight
> Sent: 26 September 2020 12:16
> To: 'syzbot' <syzbot+51177e4144d764827c45@...kaller.appspotmail.com>; linux-fsdevel@...r.kernel.org;
> linux-kernel@...r.kernel.org; syzkaller-bugs@...glegroups.com; viro@...iv.linux.org.uk
> Subject: RE: WARNING in __kernel_read (2)
> 
> > From: syzbot <syzbot+51177e4144d764827c45@...kaller.appspotmail.com>
> > Sent: 26 September 2020 03:58
> > To: linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org; syzkaller-bugs@...glegroups.com;
> > viro@...iv.linux.org.uk
> > Subject: WARNING in __kernel_read (2)
> 
> I suspect this is calling finit_module() on an fd
> that doesn't have read permissions.

Code inspection also seems to imply that the check means
the exec() also requires read permissions on the file.

This isn't traditionally true.
suid #! scripts are particularly odd without 'owner read'
(everyone except the owner can run them!).

	David

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