[Devel] Re: [Bugme-new] [Bug 12199] New: /proc/1/exe entry of PID namespace init process links to wrong executable

[Andrew Morton]

(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Thu, 11 Dec 2008 08:16:55 -0800 (PST) bugme-daemon at bugzilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=12199
> 
>            Summary: /proc/1/exe entry of PID namespace init process links to
>                     wrong executable
>            Product: Process Management
>            Version: 2.5
>      KernelVersion: 2.6.27.8
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: low
>           Priority: P1
>          Component: Other
>         AssignedTo: process_other at kernel-bugs.osdl.org
>         ReportedBy: robert.rex at exasol.com
> 
> 
> Latest working kernel version:
> 
> None known.
> 
> Earliest failing kernel version:
> 
> 2.6.25.4, 2.6.27.4 and 2.6.27.8 show this behaviour, but I assume that it
> exists since 2.6.24 with the introduction of PID namespaces.
> 
> Distribution: CentOS 5.1
> 
> Hardware Environment: x86-64
> 
> Software Environment: (see attached test program)
> 
> Problem Description:
> 
> The /proc/1/exe entry of a new PID namespace does not link to the expected
> binary if it was started within a chroot. All other processes in this namespace
> link to the expected path.
> 
> Steps to reproduce: (see attached test program)
> 
> 1) chroot() into an appropriate directory.
> 2) Create a process, which clone()s a thread in a new PID namespace with
> CLONE_NEWPID.
> 3) Mount /proc from within this new namespace.
> 3) Read the /proc/1/exe link from within this new namespace. It points to the
> "real" binary, not the (expected) link that is valid in this chroot.
> 
> The attached program executes steps 2, 3 and 4 and does a "/bin/ls -la /proc/1
> /proc/2" in the new namespace. The output below was collected with the
> following commands:
> 
> 1) mkdir /tmp/target
> 2) mount /dev/sda1 /tmp/target (/dev/sda1 is also mounted on /)
> 3) chroot /tmp/target
> 4) ./pid_namespace_chroot
> 
> ---------------
> /proc/1:
> [...]
> lrwxrwxrwx   1 root root 0 Dec 11 16:18 exe ->
> /tmp/target/root/pid_namespace_chroot
> [...]
> lrwxrwxrwx   1 root root 0 Dec 11 16:18 root -> /
> [...]
> 
> /proc/2:
> [...]
> lrwxrwxrwx   1 root root 0 Dec 11 16:18 exe -> /bin/ls
> [...]
> lrwxrwxrwx   1 root root 0 Dec 11 16:18 root -> /
> [...]
> ---------------
> 
> Hopefully, I do not miss a point, but I assume that this is not intended?!
> 

Thanks.

There's a test program attached to the bugzilla report.
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