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[ Upstream commit 16ae6aa1705299789f71fdea59bfb119c1fbd9c0 ] The TCP repair sequence of operation is to first set the socket in repair mode, then inject the TCP stats into the socket with repair socket options, then call connect() to re-activate the socket. The connect syscall simply returns and set state to ESTABLISHED mode. As a result Fast Open is meaningless for TCP repair. However allowing sendto() system call with MSG_FASTOPEN flag half-way during the repair operation could unexpectedly cause data to be sent, before the operation finishes changing the internal TCP stats (e.g. MSS). This in turn triggers TCP warnings on inconsistent packet accounting. The fix is to simply disallow Fast Open operation once the socket is in the repair mode. Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Reviewed-by: Neal Cardwell <ncardwell@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.