linux-kernel - Re: BUG: unable to handle kernel paging request from pty

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Date:	Fri, 26 Feb 2016 09:15:50 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Peter Hurley <peter@...leysoftware.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, stable@...r.kernel.org
Cc:	lwn@....net
Subject: Re: BUG: unable to handle kernel paging request from pty_write [was:
 Linux 4.4.2]

On 02/25/2016, 07:40 PM, Peter Hurley wrote:
>> This was trigerred by a gdb build on our servers [1].
> 
> I noted that the crash is not strictly for building gdb but appears
> to be with gdb running?

Yes, when gdb is built, gdb tests are run. From the build log gdb_log
[1], checks were run on the top of built gdb:
./orphanripper make -j8 -k check//unix/-m64 check//unix/-m64/-fPIC/-pie
check//unix/-m32 check//unix/-m32/-fPIC/-pie

[1] http://labs.suse.cz/jslaby/bug-968218/

> Perhaps some test that has failed?
> Maybe some ABI violation with gdb + kvm?

[  425s]                === gdb tests ===
[  425s]
[  425s] Schedule of variations:
[  425s]     unix/-m32
[  425s]
[  425s] Running target unix/-m32
[  425s] Using /usr/share/dejagnu/baseboards/unix.exp as board
description file for target.
[  425s] Using /usr/share/dejagnu/config/unix.exp as generic interface
file for target.
[  425s] Using
/home/abuild/rpmbuild/BUILD/gdb-7.10.1/gdb/testsuite/config/unix.exp as
tool-and-target-specific interface file.
[  425s] Running
/home/abuild/rpmbuild/BUILD/gdb-7.10.1/gdb/testsuite/gdb.base/break-interp.exp
...
[  425s] [  413.383880] kernel tried to execute NX-protected page -
exploit attempt? (uid: 399)


It's plenty of code run in there:
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gdb/testsuite/gdb.base/break-interp.exp;h=713e1008fb3739f7fdcdb6c0a484a46b279ef1b6;hb=HEAD

> Is this reproducible?

I tried whole day yesterday without luck :(.

thanks,
-- 
js
suse labs