Re: [NETNS]: Fix /proc/net breakage

From: Andrew Morton
Date: Wed Dec 05 2007 - 07:02:48 EST


On Mon, 3 Dec 2007 19:00:25 GMT Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx> wrote:

> Gitweb: http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=2b1e300a9dfc3196ccddf6f1d74b91b7af55e416
> Commit: 2b1e300a9dfc3196ccddf6f1d74b91b7af55e416
> Parent: e03ba84adb62fbc6049325a5bc00ef6932fa5e39
> Author: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> AuthorDate: Sun Dec 2 00:33:17 2007 +1100
> Committer: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> CommitDate: Sun Dec 2 00:33:17 2007 +1100
>
> [NETNS]: Fix /proc/net breakage
>
> Well I clearly goofed when I added the initial network namespace support
> for /proc/net. Currently things work but there are odd details visible to
> user space, even when we have a single network namespace.
>
> Since we do not cache proc_dir_entry dentries at the moment we can just
> modify ->lookup to return a different directory inode depending on the
> network namespace of the process looking at /proc/net, replacing the
> current technique of using a magic and fragile follow_link method.
>
> To accomplish that this patch:
> - introduces a shadow_proc method to allow different dentries to
> be returned from proc_lookup.
> - Removes the old /proc/net follow_link magic
> - Fixes a weakness in our not caching of proc generic dentries.
>
> As shadow_proc uses a task struct to decided which dentry to return we can
> go back later and fix the proc generic caching without modifying any code
> that uses the shadow_proc method.

This patch caused the binfmt_misc regression reported in
http://bugzilla.kernel.org/show_bug.cgi?id=9504

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