commit f658adeea4 upstream.
fuse_direct_io() can end up advancing the iterator by more than the amount
of data read or written. This case is handled by the generic code if going
through ->direct_IO(), but not in the FOPEN_DIRECT_IO case.
Fix by reverting the extra bytes from the iterator in case of error or a
short count.
To test: install lxcfs, then the following testcase
int fd = open("/var/lib/lxcfs/proc/uptime", O_RDONLY);
sendfile(1, fd, NULL, 16777216);
sendfile(1, fd, NULL, 16777216);
will spew WARN_ON() in iov_iter_pipe().
Reported-by: Peter Geis <pgwipeout@gmail.com>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 3c3db095b6 ("fuse: use iov_iter based generic splice helpers")
Cc: <stable@vger.kernel.org> # v5.1
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
07fbef9a6e