David S. Miller 5532946e33 Merge branch 'tcp-fix-handling-of-stale-syncookies-timestamps'
Guillaume Nault says:

====================
tcp: fix handling of stale syncookies timestamps

The synflood timestamps (->ts_recent_stamp and ->synq_overflow_ts) are
only refreshed when the syncookie protection triggers. Therefore, their
value can become very far apart from jiffies if no synflood happens for
a long time.

If jiffies grows too much and wraps while the synflood timestamp isn't
refreshed, then time_after32() might consider the later to be in the
future. This can trick tcp_synq_no_recent_overflow() into returning
erroneous values and rejecting valid ACKs.

Patch 1 handles the case of ACKs using legitimate syncookies.
Patch 2 handles the case of stray ACKs.
Patch 3 annotates lockless timestamp operations with READ_ONCE() and
WRITE_ONCE().

Changes from v3:
  - Fix description of time_between32() (found by Eric Dumazet).
  - Use more accurate Fixes tag in patch 3 (suggested by Eric Dumazet).

Changes from v2:
  - Define and use time_between32() instead of a pair of
    time_before32/time_after32 (suggested by Eric Dumazet).
  - Use 'last_overflow - HZ' as lower bound in
    tcp_synq_no_recent_overflow(), to accommodate for concurrent
    timestamp updates (found by Eric Dumazet).
  - Add a third patch to annotate lockless accesses to .ts_recent_stamp.

Changes from v1:
  - Initialising timestamps at socket creation time is not enough
    because jiffies wraps in 24 days with HZ=1000 (Eric Dumazet).
    Handle stale timestamps in tcp_synq_overflow() and
    tcp_synq_no_recent_overflow() instead.
  - Rework commit description.
  - Add a second patch to handle the case of stray ACKs.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
2019-12-06 21:05:14 -08:00
2019-12-06 20:52:16 -08:00
2019-11-15 14:38:27 +01:00
2019-09-22 10:34:46 -07:00
2019-11-24 16:32:01 -08:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

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.
Description
No description provided
Readme 5.7 GiB
Languages
C 97.6%
Assembly 1%
Shell 0.5%
Python 0.3%
Makefile 0.3%