aa83a2a580
syzbot reported a bug when putting the last reference to a tasks file descriptor table. Debugging this showed we didn't recalculate the current maximum fd number for CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC after we unshared the file descriptors table. So max_fd could exceed the current fdtable maximum causing us to set excessive bits. As a concrete example, let's say the user requested everything from fd 4 to ~0UL to be closed and their current fdtable size is 256 with their highest open fd being 4. With CLOSE_RANGE_UNSHARE the caller will end up with a new fdtable which has room for 64 file descriptors since that is the lowest fdtable size we accept. But now max_fd will still point to 255 and needs to be adjusted. Fix this by retrieving the correct maximum fd value in __range_cloexec(). Reported-by: syzbot+283ce5a46486d6acdbaf@syzkaller.appspotmail.com Fixes: 582f1fb6b721 ("fs, close_range: add flag CLOSE_RANGE_CLOEXEC") Fixes: fec8a6a69103 ("close_range: unshare all fds for CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC") Cc: Christoph Hellwig <hch@lst.de> Cc: Giuseppe Scrivano <gscrivan@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Cc: stable@vger.kernel.org Change-Id: Ib6aeb02d2b4556ba048cd4ca8150f9d2c29abdb3 Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.