Go to file
Eric Dumazet 431280eebe ipv4: tcp: send zero IPID for RST and ACK sent in SYN-RECV and TIME-WAIT state
tcp uses per-cpu (and per namespace) sockets (net->ipv4.tcp_sk) internally
to send some control packets.

1) RST packets, through tcp_v4_send_reset()
2) ACK packets in SYN-RECV and TIME-WAIT state, through tcp_v4_send_ack()

These packets assert IP_DF, and also use the hashed IP ident generator
to provide an IPv4 ID number.

Geoff Alexander reported this could be used to build off-path attacks.

These packets should not be fragmented, since their size is smaller than
IPV4_MIN_MTU. Only some tunneled paths could eventually have to fragment,
regardless of inner IPID.

We really can use zero IPID, to address the flaw, and as a bonus,
avoid a couple of atomic operations in ip_idents_reserve()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Geoff Alexander <alexandg@cs.unm.edu>
Tested-by: Geoff Alexander <alexandg@cs.unm.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-08-22 21:42:58 -07:00
arch Minor code cleanups for PPC. 2018-08-19 10:38:36 -07:00
block for-4.19/block-20180812 2018-08-14 10:23:25 -07:00
certs Replace magic for trusting the secondary keyring with #define 2018-08-16 09:57:20 -07:00
crypto DMAengine updates for v4.19-rc1 2018-08-18 15:55:59 -07:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-08-19 11:51:45 -07:00
drivers net: ethernet: renesas: use SPDX identifier for Renesas drivers 2018-08-22 21:37:27 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Driver core patches for 4.19-rc1 2018-08-18 11:44:53 -07:00
include net_sched: fix unused variable warning in stmmac 2018-08-22 21:40:21 -07:00
init mm: introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB 2018-08-17 16:20:30 -07:00
ipc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-08-15 15:04:25 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-08-19 11:51:45 -07:00
lib rhashtable: remove duplicated include from rhashtable.c 2018-08-20 19:18:50 -07:00
LICENSES LICENSES: Add Linux-OpenIB license text 2018-04-27 16:41:53 -06:00
mm mm/hmm.c: remove unused variables align_start and align_end 2018-08-17 16:20:33 -07:00
net ipv4: tcp: send zero IPID for RST and ACK sent in SYN-RECV and TIME-WAIT state 2018-08-22 21:42:58 -07:00
samples samples/bpf: all XDP samples should unload xdp/bpf prog on SIGTERM 2018-08-16 21:55:32 +02:00
scripts Char/Misc driver patches for 4.19-rc1 2018-08-18 11:04:51 -07:00
security Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2018-08-15 22:54:12 -07:00
sound DMAengine updates for v4.19-rc1 2018-08-18 15:55:59 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-08-19 11:51:45 -07:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt Minor code cleanups for PPC. 2018-08-19 10:38:36 -07:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap Merge branch 'linus/master' into rdma.git for-next 2018-08-16 14:21:29 -06:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2018-08-18 16:48:07 -07:00
Makefile Kconfig updates for v4.19 2018-08-15 12:50:10 -07:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

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.
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.