From: Pavel Machek <pavel@ucw.cz>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org, keescook@chromium.org,
Sean Christopherson <seanjc@google.com>
Subject: Re: [PATCH v2] x86/mm: Refuse W^X violations
Date: Sun, 2 Oct 2022 12:33:13 +0200 [thread overview]
Message-ID: <20221002095516.GA10085@duo.ucw.cz> (raw)
In-Reply-To: <4dd594ad-490a-68ee-9e32-fbd9f135bd54@intel.com>
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On Wed 2022-09-21 13:59:06, Dave Hansen wrote:
> On 9/21/22 13:07, Guenter Roeck wrote:
> > [ 2.042861] CPA refuse W^X violation: 8000000000000063 -> 0000000000000063 range: 0x00000000c00a0000 - 0x00000000c00a0fff PFN a0
> > ILLOPC: cbc65efa: 0f 0b
> > [ 2.043267] WARNING: CPU: 0 PID: 1 at arch/x86/mm/pat/set_memory.c:600 __change_page_attr_set_clr+0xdca/0xdd0
> ...
> > [ 2.050307] ---[ end trace 0000000000000000 ]---
> > [ 2.050762] PCI: PCI BIOS area is rw and x. Use pci=nobios if you want it NX.
> > [ 2.051115] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
> > [ 2.051115] BUG: unable to handle page fault for address: c00fd2bf
>
> This _looks_ like it is working as intended. The PCI BIOS code tried to
> make a RWX page. The CPA code refused to do it and presumably returned
> an error, leaving a RW page, non-executable page. The PCI code didn't
> check the set_memory_x() return code and tried to go execute anyway.
> That resulted in the oops.
>
> I was able to reproduce this pretty easily. The workaround from dmesg
> is pci=nobios. That seems to do the trick for me, although that advise
> was sandwiched between a warning and an oops, so not the easiest to find.
>
> I'm a bit torn what to do on this one. Breaking the boot is bad, but so
> is leaving RWX memory around.
Well, the original patch is bad. Boot regressions are not acceptable.
We should first add an WARN_ON(), debug and fix the failures, then we
can start refusing the transitions.
Best regards,
Pavel
--
People of Russia, stop Putin before his war on Ukraine escalates.
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next prev parent reply other threads:[~2022-10-02 10:33 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-29 10:18 Peter Zijlstra
2022-08-29 19:08 ` Kees Cook
2022-09-01 18:17 ` [tip: x86/mm] " tip-bot2 for Peter Zijlstra
2022-09-21 20:07 ` [PATCH v2] " Guenter Roeck
2022-09-21 20:59 ` Dave Hansen
2022-09-21 22:59 ` Guenter Roeck
2022-09-22 3:09 ` Guenter Roeck
2022-09-22 7:46 ` Peter Zijlstra
2022-09-22 15:00 ` Dave Hansen
2022-09-22 16:38 ` Guenter Roeck
2022-09-22 16:29 ` Guenter Roeck
2022-09-22 19:31 ` [PATCH] x86/mm+efi: Avoid creating W+X mappings Dave Hansen
2022-09-22 22:08 ` Ard Biesheuvel
2022-09-23 6:59 ` Peter Zijlstra
2022-09-23 9:49 ` Ard Biesheuvel
2022-09-23 13:58 ` Guenter Roeck
2022-09-23 14:26 ` Ard Biesheuvel
2022-09-23 18:31 ` Kees Cook
2022-09-23 19:53 ` Ard Biesheuvel
2022-09-23 21:19 ` Kees Cook
2022-09-23 22:15 ` Dave Hansen
2022-09-23 22:32 ` Eric W. Biederman
2022-09-24 0:04 ` Kees Cook
2022-10-02 10:33 ` Pavel Machek [this message]
2022-10-24 15:27 ` [PATCH v2] x86/mm: Refuse W^X violations Steven Rostedt
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