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


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