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5532946e33
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>
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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.