Regression - Xorg start failed

Regression - Xorg start failed

[Dave Young]

Hi

With kernel built from current linus's tree, I can not start xorg,
it failed with:

Backtrace:
0: X(xorg_backtrace+0x26) [0x4e8bb6]
1: X(xf86SigHandler+0x39) [0x489989]
2: /lib64/libc.so.6 [0x7f077a6b9f30]
3: /usr/lib64/libpciaccess.so.0(pci_device_get_bridge_buses+0xf1) [0x7f077c101fd1]
4: X(initPciBusState+0x8d) [0x470abd]
5: X(xf86AccessInit+0xe) [0x48e26e]
6: X(InitOutput+0x108b) [0x466bfb]
7: X(main+0x20e) [0x42ceee]
8: /lib64/libc.so.6(__libc_start_main+0xe6) [0x7f077a6a5526]
9: X [0x42c529]

Fatal server error:
Caught signal 11.  Server aborting

The graphic driver I used is intel (i915)

Finally I bisected it, results:
47970b1b2aa64464bc0a9543e86361a622ae7c03 is first bad commit
commit 47970b1b2aa64464bc0a9543e86361a622ae7c03
Author: Chris Wright <chrisw@sous-sol.org>
Date:   Thu Feb 10 15:58:56 2011 -0800

    pci: use security_capable() when checking capablities during config space read
    
    Eric Paris noted that commit de139a3 ("pci: check caps from sysfs file
    open to read device dependent config space") caused the capability check
    to bypass security modules and potentially auditing.  Rectify this by
    calling security_capable() when checking the open file's capabilities
    for config space reads.
    
    Reported-by: Eric Paris <eparis@redhat.com>
    Signed-off-by: Chris Wright <chrisw@sous-sol.org>
    Signed-off-by: James Morris <jmorris@namei.org>

:040000 040000 e14ad9470ca5f84f13cd31eaf5def16d40bc54f1 cbf987647b8052214dd928c87c6becfb639e4ca2 M      drivers

Any idea?

--
Thanks
Dave

Re: Regression - Xorg start failed

[Dave Airlie]

On Sun, Feb 13, 2011 at 4:22 PM, Dave Young <hidave.darkstar@gmail.com> wrote:
> Hi
>
> With kernel built from current linus's tree, I can not start xorg,
> it failed with:

Me too!,

Thanks for bisceting this, I just tried -rc4 on my Fedora 13 laptop
and wasn't looking forward to bisecting it.

If this isn't hitting later distros its probably an updated
libpciaccess that fixed something.

libpciaccess-0.10.9-2.20091209.fc13.i686 is what is on this box.

Probably should revert first, then work out what is crapping out libpciaccess.

Dave.

Re: Regression - Xorg start failed

[Linus Torvalds]

On Sat, Feb 12, 2011 at 11:53 PM, Dave Airlie <airlied@gmail.com> wrote:
>
> Probably should revert first, then work out what is crapping out libpciaccess.

Yeah, I'll revert. The patch is one of those "obviously a good idea,
but in practice it's not something we can change now".

                      Linus

Re: Regression - Xorg start failed

[Chris Wright]

* Linus Torvalds (torvalds@linux-foundation.org) wrote:
> On Sat, Feb 12, 2011 at 11:53 PM, Dave Airlie <airlied@gmail.com> wrote:
> > Probably should revert first, then work out what is crapping out libpciaccess.
> 
> Yeah, I'll revert. The patch is one of those "obviously a good idea,
> but in practice it's not something we can change now".

Turns out I'm just a bona fide idiot.

I was not testing the right kernel _and_ didn't get the logic right.

sorry for the screw up,
-chris
---

Subject: [PATCH] pci: use security_capable correctly during config space read

Commit 47970b1 ("pci: use security_capable() when checking capablities
during config space read") is just plain broken.  The normal capable()
interface returns true on success, but the LSM interface returns 0 on
success.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---

I've tested this quickly (lspci behaviour is as expected).

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index f7771f3..ea25e5b 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -369,7 +369,7 @@ pci_read_config(struct file *filp, struct kobject *kobj,
 	u8 *data = (u8*) buf;
 
 	/* Several chips lock up trying to read undefined config space */
-	if (security_capable(filp->f_cred, CAP_SYS_ADMIN)) {
+	if (security_capable(filp->f_cred, CAP_SYS_ADMIN) == 0) {
 		size = dev->cfg_size;
 	} else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
 		size = 128;

Re: Regression - Xorg start failed

[James Morris]

On Sun, 13 Feb 2011, Chris Wright wrote:

> Subject: [PATCH] pci: use security_capable correctly during config space read
> 
> Commit 47970b1 ("pci: use security_capable() when checking capablities
> during config space read") is just plain broken.  The normal capable()
> interface returns true on success, but the LSM interface returns 0 on
> success.
> 
> Signed-off-by: Chris Wright <chrisw@sous-sol.org>

Sorry, I should have caught this.

Acked-by: James Morris <jmorris@namei.org>

> ---
> 
> I've tested this quickly (lspci behaviour is as expected).
> 
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index f7771f3..ea25e5b 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -369,7 +369,7 @@ pci_read_config(struct file *filp, struct kobject *kobj,
>  	u8 *data = (u8*) buf;
>  
>  	/* Several chips lock up trying to read undefined config space */
> -	if (security_capable(filp->f_cred, CAP_SYS_ADMIN)) {
> +	if (security_capable(filp->f_cred, CAP_SYS_ADMIN) == 0) {
>  		size = dev->cfg_size;
>  	} else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
>  		size = 128;
> 
> 

-- 
James Morris
<jmorris@namei.org>

[PATCH v3] pci: use security_capable() when checking capablities during config space read

[Chris Wright]

This reintroduces commit 47970b1b which was subsequently reverted
as f00eaeea.  The original change was broken and caused X startup
failures and generally made privileged processes incapable of reading
device dependent config space.  The normal capable() interface returns
true on success, but the LSM interface returns 0 on success.  This thinko
is now fixed in this patch, and has been confirmed to work properly.

So, once again...Eric Paris noted that commit de139a3 ("pci: check caps
from sysfs file open to read device dependent config space") caused the
capability check to bypass security modules and potentially auditing.
Rectify this by calling security_capable() when checking the open file's
capabilities for config space reads.

Reported-by: Eric Paris <eparis@redhat.com>
Tested-by: Dave Young <hidave.darkstar@gmail.com>
Acked-by: James Morris <jmorris@namei.org>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Alex Riesen <raa.lkml@gmail.com>
Cc: Sedat Dilek <sedat.dilek@googlemail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
v2: added Reported-by Eric
v3: fix logic screw up

 drivers/pci/pci-sysfs.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 8ecaac9..ea25e5b 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -23,6 +23,7 @@
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include <linux/capability.h>
+#include <linux/security.h>
 #include <linux/pci-aspm.h>
 #include <linux/slab.h>
 #include "pci.h"
@@ -368,7 +369,7 @@ pci_read_config(struct file *filp, struct kobject *kobj,
 	u8 *data = (u8*) buf;
 
 	/* Several chips lock up trying to read undefined config space */
-	if (cap_raised(filp->f_cred->cap_effective, CAP_SYS_ADMIN)) {
+	if (security_capable(filp->f_cred, CAP_SYS_ADMIN) == 0) {
 		size = dev->cfg_size;
 	} else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
 		size = 128;
-- 
1.7.3.4

Re: [PATCH v3] pci: use security_capable() when checking capablities during config space read

[James Morris]

Also pullable from here:

The following changes since commit 795abaf1e4e188c4171e3cd3dbb11a9fcacaf505:
  David Miller (1):
        klist: Fix object alignment on 64-bit.

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6 for-linus

Chris Wright (1):
      pci: use security_capable() when checking capablities during config space read

 drivers/pci/pci-sysfs.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

-- 
James Morris
<jmorris@namei.org>

Re: [PATCH v3] pci: use security_capable() when checking capablities during config space read

[Alex Riesen]

On Tue, Feb 15, 2011 at 02:21, Chris Wright <chrisw@sous-sol.org> wrote:
> This reintroduces commit 47970b1b which was subsequently reverted
> as f00eaeea.  The original change was broken and caused X startup
> failures and generally made privileged processes incapable of reading
> device dependent config space.  The normal capable() interface returns
> true on success, but the LSM interface returns 0 on success.  This thinko
> is now fixed in this patch, and has been confirmed to work properly.
>
> So, once again...Eric Paris noted that commit de139a3 ("pci: check caps
> from sysfs file open to read device dependent config space") caused the
> capability check to bypass security modules and potentially auditing.
> Rectify this by calling security_capable() when checking the open file's
> capabilities for config space reads.
>
> Reported-by: Eric Paris <eparis@redhat.com>
> Tested-by: Dave Young <hidave.darkstar@gmail.com>
> Acked-by: James Morris <jmorris@namei.org>
> Cc: Dave Airlie <airlied@gmail.com>
> Cc: Alex Riesen <raa.lkml@gmail.com>
> Cc: Sedat Dilek <sedat.dilek@googlemail.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Chris Wright <chrisw@sous-sol.org>

FWIW, I confirm the fix.

Re: Regression - Xorg start failed

[Dave Young]

On Sun, Feb 13, 2011 at 04:35:31PM -0800, Chris Wright wrote:
> * Linus Torvalds (torvalds@linux-foundation.org) wrote:
> > On Sat, Feb 12, 2011 at 11:53 PM, Dave Airlie <airlied@gmail.com> wrote:
> > > Probably should revert first, then work out what is crapping out libpciaccess.
> > 
> > Yeah, I'll revert. The patch is one of those "obviously a good idea,
> > but in practice it's not something we can change now".
> 
> Turns out I'm just a bona fide idiot.
> 
> I was not testing the right kernel _and_ didn't get the logic right.
> 
> sorry for the screw up,
> -chris
> ---
> 
> Subject: [PATCH] pci: use security_capable correctly during config space read
> 
> Commit 47970b1 ("pci: use security_capable() when checking capablities
> during config space read") is just plain broken.  The normal capable()
> interface returns true on success, but the LSM interface returns 0 on
> success.

Chris, linus has reverted the original commit, so this does not apply.

Anyway I have tested this one, it works well. Feel free add my Tested-by line.

> 
> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
> ---
> 
> I've tested this quickly (lspci behaviour is as expected).
> 
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index f7771f3..ea25e5b 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -369,7 +369,7 @@ pci_read_config(struct file *filp, struct kobject *kobj,
>  	u8 *data = (u8*) buf;
>  
>  	/* Several chips lock up trying to read undefined config space */
> -	if (security_capable(filp->f_cred, CAP_SYS_ADMIN)) {
> +	if (security_capable(filp->f_cred, CAP_SYS_ADMIN) == 0) {
>  		size = dev->cfg_size;
>  	} else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
>  		size = 128;
> 
> 

Re: Regression - Xorg start failed

[Chris Wright]

* Dave Young (hidave.darkstar@gmail.com) wrote:
> On Sun, Feb 13, 2011 at 04:35:31PM -0800, Chris Wright wrote:
> > Commit 47970b1 ("pci: use security_capable() when checking capablities
> > during config space read") is just plain broken.  The normal capable()
> > interface returns true on success, but the LSM interface returns 0 on
> > success.
> 
> Chris, linus has reverted the original commit, so this does not apply.

Right, I'll send a new patch to James.

> Anyway I have tested this one, it works well. Feel free add my Tested-by line.

Thanks for confirming the fix Dave.

thanks,
-chris

Re: Regression - Xorg start failed

[Chris Wright]

* Dave Airlie (airlied@gmail.com) wrote:
> On Sun, Feb 13, 2011 at 4:22 PM, Dave Young <hidave.darkstar@gmail.com> wrote:
> > With kernel built from current linus's tree, I can not start xorg,
> > it failed with:
> 
> Me too!,
> 
> Thanks for bisceting this, I just tried -rc4 on my Fedora 13 laptop
> and wasn't looking forward to bisecting it.
> 
> If this isn't hitting later distros its probably an updated
> libpciaccess that fixed something.
> 
> libpciaccess-0.10.9-2.20091209.fc13.i686 is what is on this box.
> 
> Probably should revert first, then work out what is crapping out libpciaccess.

Are you running with SELinux enabled, if so can you paste the AVC error?
It's working for me here.

thanks,
-chris

Re: Regression - Xorg start failed

[Dave Airlie]

On Mon, Feb 14, 2011 at 9:31 AM, Chris Wright <chrisw@sous-sol.org> wrote:
> * Dave Airlie (airlied@gmail.com) wrote:
>> On Sun, Feb 13, 2011 at 4:22 PM, Dave Young <hidave.darkstar@gmail.com> wrote:
>> > With kernel built from current linus's tree, I can not start xorg,
>> > it failed with:
>>
>> Me too!,
>>
>> Thanks for bisceting this, I just tried -rc4 on my Fedora 13 laptop
>> and wasn't looking forward to bisecting it.
>>
>> If this isn't hitting later distros its probably an updated
>> libpciaccess that fixed something.
>>
>> libpciaccess-0.10.9-2.20091209.fc13.i686 is what is on this box.
>>
>> Probably should revert first, then work out what is crapping out libpciaccess.
>
> Are you running with SELinux enabled, if so can you paste the AVC error?
> It's working for me here.

Yes most likely, I'm not at the machine now but I'll see if I can the
AVC off it later.

On Fedora 13?

F14/rawhide seem fine.

Dave.

Re: Regression - Xorg start failed

[Chris Wright]

* Dave Airlie (airlied@gmail.com) wrote:
> Yes most likely, I'm not at the machine now but I'll see if I can the
> AVC off it later.

Great, thanks.

> On Fedora 13?
> 
> F14/rawhide seem fine.

I'm on F14.

Re: Regression - Xorg start failed

[Alex Riesen]

On Sun, Feb 13, 2011 at 07:22, Dave Young <hidave.darkstar@gmail.com> wrote:
> Finally I bisected it, results:
> 47970b1b2aa64464bc0a9543e86361a622ae7c03 is first bad commit
> commit 47970b1b2aa64464bc0a9543e86361a622ae7c03
> Author: Chris Wright <chrisw@sous-sol.org>
> Date:   Thu Feb 10 15:58:56 2011 -0800
>
>    pci: use security_capable() when checking capablities during config space read
>
>    Eric Paris noted that commit de139a3 ("pci: check caps from sysfs file
>    open to read device dependent config space") caused the capability check
>    to bypass security modules and potentially auditing.  Rectify this by
>    calling security_capable() when checking the open file's capabilities
>    for config space reads.
>
>    Reported-by: Eric Paris <eparis@redhat.com>
>    Signed-off-by: Chris Wright <chrisw@sous-sol.org>
>    Signed-off-by: James Morris <jmorris@namei.org>
>

Actually, even reading the PCI capabilities fails with lspci
reporting "Capabilities: <access denied>" if run as root.
"libpciaccess" should have handled this situation, but still
it looks like a regression and it breaks existing systems.