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

Seth Forshee
2014-09-02T15:45:05Z

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>
---
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