Re: [PATCH v2 2/3] fuse: Translate pids passed to userspace into pid namespaces

Serge Hallyn
2014-09-05T17:11:24Z

Quoting Seth Forshee (seth.forshee@canonical.com):
> If the process reading on the fuse fd is executing in a pid
> namespace then giving it the global pid of the process making
> a request doesn't make sense. Instead, capture the pid namespace
> when the filesystem is first mounted and translate pids into this
> namespace before passing them to userspace.
>
> Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

> ---
> fs/fuse/dev.c | 9 +++++----
> fs/fuse/fuse_i.h | 4 ++++
> fs/fuse/inode.c | 3 +++
> 3 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index ca887314aba9..839caebd34f1 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -20,6 +20,7 @@
> #include <linux/swap.h>
> #include <linux/splice.h>
> #include <linux/aio.h>
> +#include <linux/sched.h>
>
> MODULE_ALIAS_MISCDEV(FUSE_MINOR);
> MODULE_ALIAS("devname:fuse");
> @@ -124,11 +125,11 @@ static void __fuse_put_request(struct fuse_req *req)
> atomic_dec(&req->count);
> }
>
> -static void fuse_req_init_context(struct fuse_req *req)
> +static void fuse_req_init_context(struct fuse_conn *fc, struct fuse_req *req)
> {
> req->in.h.uid = from_kuid_munged(&init_user_ns, current_fsuid());
> req->in.h.gid = from_kgid_munged(&init_user_ns, current_fsgid());
> - req->in.h.pid = current->pid;
> + req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);
> }
>
> static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background)
> @@ -168,7 +169,7 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
> goto out;
> }
>
> - fuse_req_init_context(req);
> + fuse_req_init_context(fc, req);
> req->waiting = 1;
> req->background = for_background;
> return req;
> @@ -257,7 +258,7 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
> if (!req)
> req = get_reserved_req(fc, file);
>
> - fuse_req_init_context(req);
> + fuse_req_init_context(fc, req);
> req->waiting = 1;
> req->background = 0;
> return req;
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index e8e47a6ab518..a3ded071e2c6 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -22,6 +22,7 @@
> #include <linux/rbtree.h>
> #include <linux/poll.h>
> #include <linux/workqueue.h>
> +#include <linux/pid_namespace.h>
>
> /** Max number of pages that can be used in a single read request */
> #define FUSE_MAX_PAGES_PER_REQ 32
> @@ -386,6 +387,9 @@ struct fuse_conn {
> /** The group id for this mount */
> kgid_t group_id;
>
> + /** The pid namespace for this mount */
> + struct pid_namespace *pid_ns;
> +
> /** The fuse mount flags for this mount */
> unsigned flags;
>
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 03246cd9d47a..c6d8473b1a80 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -20,6 +20,7 @@
> #include <linux/random.h>
> #include <linux/sched.h>
> #include <linux/exportfs.h>
> +#include <linux/pid_namespace.h>
>
> MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
> MODULE_DESCRIPTION("Filesystem in Userspace");
> @@ -616,6 +617,7 @@ void fuse_conn_init(struct fuse_conn *fc)
> fc->initialized = 0;
> fc->attr_version = 1;
> get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
> + fc->pid_ns = get_pid_ns(task_active_pid_ns(current));
> }
> EXPORT_SYMBOL_GPL(fuse_conn_init);
>
> @@ -953,6 +955,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
>
> static void fuse_free_conn(struct fuse_conn *fc)
> {
> + put_pid_ns(fc->pid_ns);
> kfree_rcu(fc, rcu);
> }
>
> --
> 1.9.1
>