2017-06-09 00:32:40

by Andrei Vagin

Subject: [PATCH] fs: don't forget to put old mntns in mntns_install

Fixes: 4f757f3cbf54 ("make sure that mntns_install() doesn't end up with referral for root")
Cc: Al Viro <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
---
fs/namespace.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/namespace.c b/fs/namespace.c
index 8bd3e4d..5a44384 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3488,6 +3488,8 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
return err;
}

+ put_mnt_ns(old_mnt_ns);
+
/* Update the pwd and root */
set_fs_pwd(fs, &root);
set_fs_root(fs, &root);
--
2.9.4

2017-06-16 20:41:29

by Andrei Vagin

Subject: Re: [PATCH] fs: don't forget to put old mntns in mntns_install

Hi Alexander,

Do you have any comments about this patch?

Here is a reproducer for this leak:

$ cat mount.sh
set -e -x
mount --make-rprivate /
mount -t tmpfs zdtm /mnt
mount --make-shared /mnt
mount -t proc procX /proc
for i in `seq $1`; do
mount --bind /mnt /mnt
done
mount --make-rprivate /mnt
unshare -m sleep 1000 &
pid=$!
unshare -m nsenter -m -t $pid nsenter -m -t $$ true


$ while :; do unshare -Umpfr sh mount.sh 16 || break; done

...

$ cat /proc/slabinfo | grep mnt
mnt_cache 3281745 3281776 512 16 2 : tunables 0 0 0 : slabdata 205111 205111 0


On Thu, Jun 08, 2017 at 05:32:29PM -0700, Andrei Vagin wrote:
> Fixes: 4f757f3cbf54 ("make sure that mntns_install() doesn't end up with referral for root")
> Cc: Al Viro <[email protected]>
> Signed-off-by: Andrei Vagin <[email protected]>
> ---
> fs/namespace.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 8bd3e4d..5a44384 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -3488,6 +3488,8 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
> return err;
> }
>
> + put_mnt_ns(old_mnt_ns);
> +
> /* Update the pwd and root */
> set_fs_pwd(fs, &root);
> set_fs_root(fs, &root);
> --
> 2.9.4
>