From 5d6d3a301c4e749e04be6fcdcf4cb1ffa8bae524 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Tue, 12 Sep 2017 16:57:53 +0200 Subject: [PATCH] fuse: allow server to run in different pid_ns Commit 0b6e9ea041e6 ("fuse: Add support for pid namespaces") broke Sandstorm.io development tools, which have been sending FUSE file descriptors across PID namespace boundaries since early 2014. The above patch added a check that prevented I/O on the fuse device file descriptor if the pid namespace of the reader/writer was different from the pid namespace of the mounter. With this change passing the device file descriptor to a different pid namespace simply doesn't work. The check was added because pids are transferred to/from the fuse userspace server in the namespace registered at mount time. To fix this regression, remove the checks and do the following: 1) the pid in the request header (the pid of the task that initiated the filesystem operation) is translated to the reader's pid namespace. If a mapping doesn't exist for this pid, then a zero pid is used. Note: even if a mapping would exist between the initiator task's pid namespace and the reader's pid namespace the pid will be zero if either mapping from initator's to mounter's namespace or mapping from mounter's to reader's namespace doesn't exist. 2) The lk.pid value in setlk/setlkw requests and getlk reply is left alone. Userspace should not interpret this value anyway. Also allow the setlk/setlkw operations if the pid of the task cannot be represented in the mounter's namespace (pid being zero in that case). Reported-by: Kenton Varda Signed-off-by: Miklos Szeredi Fixes: 0b6e9ea041e6 ("fuse: Add support for pid namespaces") Cc: # v4.12+ Cc: Eric W. Biederman Cc: Seth Forshee --- fs/fuse/dev.c | 13 +++++++------ fs/fuse/file.c | 3 --- 2 files changed, 7 insertions(+), 9 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index c16d00e53264..13c65dd2d37d 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1222,9 +1222,6 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, struct fuse_in *in; unsigned reqsize; - if (task_active_pid_ns(current) != fc->pid_ns) - return -EIO; - restart: spin_lock(&fiq->waitq.lock); err = -EAGAIN; @@ -1262,6 +1259,13 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, in = &req->in; reqsize = in->h.len; + + if (task_active_pid_ns(current) != fc->pid_ns) { + rcu_read_lock(); + in->h.pid = pid_vnr(find_pid_ns(in->h.pid, fc->pid_ns)); + rcu_read_unlock(); + } + /* If request is too large, reply with an error and restart the read */ if (nbytes < reqsize) { req->out.h.error = -EIO; @@ -1823,9 +1827,6 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud, struct fuse_req *req; struct fuse_out_header oh; - if (task_active_pid_ns(current) != fc->pid_ns) - return -EIO; - if (nbytes < sizeof(struct fuse_out_header)) return -EINVAL; diff --git a/fs/fuse/file.c b/fs/fuse/file.c index ab60051be6e5..6d8e65cec01a 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2181,9 +2181,6 @@ static int fuse_setlk(struct file *file, struct file_lock *fl, int flock) if ((fl->fl_flags & FL_CLOSE_POSIX) == FL_CLOSE_POSIX) return 0; - if (pid && pid_nr == 0) - return -EOVERFLOW; - fuse_lk_fill(&args, file, fl, opcode, pid_nr, flock, &inarg); err = fuse_simple_request(fc, &args);