Re: [PATCH] pidns: Fix a leak in /proc inodes and dentries

[Eric W. Biederman]

Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx> writes:

> Fix a leak in /proc dentries and inodes with pid namespaces.
>
> This fix reverts the commit 7766755a2f249e7e0. The leak was reported by
> Daniel Lezcano - see  http://lkml.org/lkml/2009/10/2/159.
>
> To summarize the thread, when container-init is terminated, it sets the
> PF_EXITING flag and then zaps all the other processes in the container.
> When those processes exit, they are expected to be reaped by the container-
> init and as a part of reaping, the container-init should flush any /proc
> dentries associated with the processes. But because the container-init is
> itself exiting and the following PF_EXITING check, the dentires are not
> flushed, resulting in leak in /proc inodes and dentries.

Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

> Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx>
> Reported-by: Daniel Lezcano <dlezcano@xxxxxxxxxx>
> Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxx>
> Cc: Andrea Arcangeli <andrea@xxxxxxxxxxxx>
>
> ---
>  fs/proc/base.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> Index: linux-2.6/fs/proc/base.c
> ===================================================================
> --- linux-2.6.orig/fs/proc/base.c	2009-10-19 20:28:51.000000000 -0700
> +++ linux-2.6/fs/proc/base.c	2009-10-19 20:29:03.000000000 -0700
> @@ -2580,8 +2580,7 @@ static void proc_flush_task_mnt(struct v
>  	name.len = snprintf(buf, sizeof(buf), "%d", pid);
>  	dentry = d_hash_and_lookup(mnt->mnt_root, &name);
>  	if (dentry) {
> -		if (!(current->flags & PF_EXITING))
> -			shrink_dcache_parent(dentry);
> +		shrink_dcache_parent(dentry);
>  		d_drop(dentry);
>  		dput(dentry);
>  	}
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