RE: WARNING in __kernel_read (2)

[David Laight]

From: David Laight
> Sent: 26 September 2020 12:16
> To: 'syzbot' <syzbot+51177e4144d764827c45@xxxxxxxxxxxxxxxxxxxxxxxxx>; linux-fsdevel@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; syzkaller-bugs@xxxxxxxxxxxxxxxx; viro@xxxxxxxxxxxxxxxxxx
> Subject: RE: WARNING in __kernel_read (2)
> 
> > From: syzbot <syzbot+51177e4144d764827c45@xxxxxxxxxxxxxxxxxxxxxxxxx>
> > Sent: 26 September 2020 03:58
> > To: linux-fsdevel@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; syzkaller-bugs@xxxxxxxxxxxxxxxx;
> > viro@xxxxxxxxxxxxxxxxxx
> > 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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