fuse: set FR_SENT while locked

BugLink: https://bugs.launchpad.net/bugs/1824553
Otherwise fuse_dev_do_write() could come in and finish off the request, and
the set_bit(FR_SENT, ...) could trigger the WARN_ON(test_bit(FR_SENT, ...))
in request_end().

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reported-by: syzbot+ef054c4d3f64cd7f7cec@syzkaller.appspotmai
Fixes: 46c34a348b0a ("fuse: no fc->lock for pqueue parts")
Cc: <stable@vger.kernel.org> # v4.2
(cherry picked from commit 4c316f2f3ff315cb48efb7435621e5bfb81df96d)
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index f78311fa889d87f452f2d1ad7aabf6a3e440bab8..ffcfc0ae3fcfe5c7406c6d9e6f75f406f785b56b 100644 (file)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1317,8 +1317,8 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
        }
        list_move_tail(&req->list, &fpq->processing);
        __fuse_get_request(req);
-       spin_unlock(&fpq->lock);
        set_bit(FR_SENT, &req->flags);
+       spin_unlock(&fpq->lock);
        /* matches barrier in request_wait_answer() */
        smp_mb__after_atomic();
        if (test_bit(FR_INTERRUPTED, &req->flags))