Re: [PATCH -mm 7/8] user_ns: handle file sigio

["Serge E. Hallyn" <serue@us.ibm.com>]

Quoting Andrew Morton (akpm@osdl.org):
> On Thu, 4 Jan 2007 12:12:57 -0600
> "Serge E. Hallyn" <serue@us.ibm.com> wrote:
> 
> > A process in one user namespace could set a fowner and sigio on a file in a
> > shared vfsmount, ending up killing a task in another user namespace.
> >
> > Prevent this by adding a user namespace pointer to the fown_struct, and
> > enforcing that a process causing a signal to be sent be in the same
> > user namespace as the file owner.
> 
> This patch breaks the X server (stock FC5 install) with CONFIG_USER_NS=n.
> Neither the USB mouse nor the trackpad work.  They work OK under GPM.
> 
> Setting CONFIG_USER_NS=y "fixes" this.  This bug was not observed in
> 2.6.20-rc3-mm1 because that kernel had user-ns-always-on.patch for other
> reasons.  (I'll restore that patch).
> 
> There's nothing very interesting here:
> 
> 
> sony:/home/akpm> diff -u Xorg.0.log.good Xorg.0.log.bad
> --- Xorg.0.log.good     2007-01-11 21:11:11.000000000 -0800
> +++ Xorg.0.log.bad      2007-01-11 21:17:31.000000000 -0800
> @@ -6,7 +6,7 @@
>  Release Date: 21 December 2005
>  X Protocol Version 11, Revision 0, Release 7.0
>  Build Operating System:Linux 2.6.9-22.18.bz155725.ELsmp i686Red Hat, Inc.
> -Current Operating System: Linux sony 2.6.20-rc4-mm1 #15 Thu Jan 11 21:07:58 PST 2007 i686
> +Current Operating System: Linux sony 2.6.20-rc4-mm1 #16 Thu Jan 11 21:14:03 PST 2007 i686
>  Build Date: 22 March 2006
>         Before reporting problems, check http://wiki.x.org
>         to make sure that you have the latest version.
> @@ -14,7 +14,7 @@
>  Markers: (--) probed, (**) from config file, (==) default setting,
>         (++) from command line, (!!) notice, (II) informational,
>         (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
> -(==) Log file: "/var/log/Xorg.0.log", Time: Thu Jan 11 21:10:16 2007
> +(==) Log file: "/var/log/Xorg.0.log", Time: Thu Jan 11 21:16:39 2007
>  (==) Using config file: "/etc/X11/xorg.conf"
>  (==) ServerLayout "single head configuration"
>  (**) |-->Screen "Screen0" (0)
> @@ -2117,9 +2117,9 @@
>  (II) I810(0): Allocated 128 kB for the ring buffer at 0x0
>  (II) I810(0): Allocating at least 256 scanlines for pixmap cache
>  (II) I810(0): Initial framebuffer allocation size: 12288 kByte
> -(II) I810(0): Allocated 4 kB for HW cursor at 0xffff000 (0x35dd3000)
> -(II) I810(0): Allocated 16 kB for HW (ARGB) cursor at 0xfffb000 (0x35e78000)
> -(II) I810(0): Allocated 4 kB for Overlay registers at 0xfffa000 (0x35e39000).
> +(II) I810(0): Allocated 4 kB for HW cursor at 0xffff000 (0x358d5000)
> +(II) I810(0): Allocated 16 kB for HW (ARGB) cursor at 0xfffb000 (0x35888000)
> +(II) I810(0): Allocated 4 kB for Overlay registers at 0xfffa000 (0x358d7000).
>  (II) I810(0): Allocated 64 kB for the scratch buffer at 0xffea000
>  drmOpenDevice: node name is /dev/dri/card0
>  drmOpenDevice: open result is -1, (No such device or address)
> @@ -2137,8 +2137,8 @@
>  (II) I810(0): [drm] loaded kernel module for "i915" driver
>  (II) I810(0): [drm] DRM interface version 1.3
>  (II) I810(0): [drm] created "i915" driver at busid "pci:0000:00:02.0"
> -(II) I810(0): [drm] added 8192 byte SAREA at 0xf8e46000
> -(II) I810(0): [drm] mapped SAREA 0xf8e46000 to 0xb7eec000
> +(II) I810(0): [drm] added 8192 byte SAREA at 0xf8d4a000
> +(II) I810(0): [drm] mapped SAREA 0xf8d4a000 to 0xb7f23000
>  (II) I810(0): [drm] framebuffer handle = 0xc0020000
>  (II) I810(0): [drm] added 1 reserved context for kernel
>  (II) I810(0): Allocated 32 kB for the logical context at 0xffe2000.

I can't see any reason for this in the code or comparative ltp runs.
Cedric is testing on a fc6 laptop, hopefully he can reproduce it.

thanks,
-serge
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