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Eric Dumazet b617158dc0 tcp: be more careful in tcp_fragment()
Some applications set tiny SO_SNDBUF values and expect
TCP to just work. Recent patches to address CVE-2019-11478
broke them in case of losses, since retransmits might
be prevented.

We should allow these flows to make progress.

This patch allows the first and last skb in retransmit queue
to be split even if memory limits are hit.

It also adds the some room due to the fact that tcp_sendmsg()
and tcp_sendpage() might overshoot sk_wmem_queued by about one full
TSO skb (64KB size). Note this allowance was already present
in stable backports for kernels < 4.15

Note for < 4.15 backports :
 tcp_rtx_queue_tail() will probably look like :

static inline struct sk_buff *tcp_rtx_queue_tail(const struct sock *sk)
{
	struct sk_buff *skb = tcp_send_head(sk);

	return skb ? tcp_write_queue_prev(sk, skb) : tcp_write_queue_tail(sk);
}

Fixes: f070ef2ac6 ("tcp: tcp_fragment() should apply sane memory limits")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrew Prout <aprout@ll.mit.edu>
Tested-by: Andrew Prout <aprout@ll.mit.edu>
Tested-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Tested-by: Michal Kubecek <mkubecek@suse.cz>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Christoph Paasch <cpaasch@apple.com>
Cc: Jonathan Looney <jtl@netflix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-07-21 20:41:24 -07:00
arch arch/csky patches for 5.3-rc1 2019-07-19 12:15:33 -07:00
block docs conversion for v5.3-rc1 2019-07-16 12:21:41 -07:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto USB / PHY patches for 5.3-rc1 2019-07-11 15:40:06 -07:00
Documentation Remove references to dead website. 2019-07-19 12:22:04 -07:00
drivers hv_netvsc: Fix extra rcu_read_unlock in netvsc_recv_callback() 2019-07-21 20:40:28 -07:00
fs Also new for 5.3: 2019-07-19 11:38:12 -07:00
include tcp: be more careful in tcp_fragment() 2019-07-21 20:41:24 -07:00
init Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
ipc Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
kernel Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2019-07-19 12:23:37 -07:00
lib Merge branch 'akpm' (patches from Andrew) 2019-07-17 08:58:04 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
net tcp: be more careful in tcp_fragment() 2019-07-21 20:41:24 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-07-19 10:06:06 -07:00
scripts Merge branch 'akpm' (patches from Andrew) 2019-07-17 08:58:04 -07:00
security Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
sound sound fixes for 5.3-rc1 2019-07-18 09:36:51 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-07-19 10:06:06 -07:00
usr docs: early-userspace: move to driver-api guide 2019-07-15 11:03:01 -03:00
virt ARM: 2019-07-12 15:35:14 -07:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore .gitignore: exclude .get_maintainer.ignore and .gitattributes 2019-05-18 11:49:54 +09:00
.mailmap MAINTAINERS: Update my email address 2019-06-18 14:37:27 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Remove references to dead website. 2019-07-19 12:22:04 -07:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS drm fixes for -rc1: 2019-07-19 12:29:43 -07:00
Makefile Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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.

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.