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Deepa Dinamani a912b531d8 sock: Make sock->sk_stamp thread-safe
[ Upstream commit 3a0ed3e961 ]

Al Viro mentioned (Message-ID
<20170626041334.GZ10672@ZenIV.linux.org.uk>)
that there is probably a race condition
lurking in accesses of sk_stamp on 32-bit machines.

sock->sk_stamp is of type ktime_t which is always an s64.
On a 32 bit architecture, we might run into situations of
unsafe access as the access to the field becomes non atomic.

Use seqlocks for synchronization.
This allows us to avoid using spinlocks for readers as
readers do not need mutual exclusion.

Another approach to solve this is to require sk_lock for all
modifications of the timestamps. The current approach allows
for timestamps to have their own lock: sk_stamp_lock.
This allows for the patch to not compete with already
existing critical sections, and side effects are limited
to the paths in the patch.

The addition of the new field maintains the data locality
optimizations from
commit 9115e8cd2a ("net: reorganize struct sock for better data
locality")

Note that all the instances of the sk_stamp accesses
are either through the ioctl or the syscall recvmsg.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2019-01-09 17:45:51 +01:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc 2018-12-21 14:23:57 -08:00
block block: Fix null_blk_zoned creation failure with small number of zones 2018-12-11 16:19:38 -07:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: user - Disable statistics interface 2018-12-07 13:56:08 +08:00
Documentation XArray updates for 4.20-rc7 2018-12-13 16:35:58 -08:00
drivers net/wan: fix a double free in x25_asy_open_tty() 2019-01-09 17:45:50 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-12-23 10:40:41 -08:00
include sock: Make sock->sk_stamp thread-safe 2019-01-09 17:45:51 +01:00
init psi: fix reference to kernel commandline enable 2018-12-14 15:05:45 -08:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel panic: avoid deadlocks in re-entrant console drivers 2019-01-09 17:45:49 +01:00
lib XArray: Fix xa_alloc when id exceeds max 2018-12-13 14:07:33 -05:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm mm, page_alloc: fix has_unmovable_pages for HugePages 2018-12-21 14:51:18 -08:00
net sock: Make sock->sk_stamp thread-safe 2019-01-09 17:45:51 +01:00
samples VFIO updates for v4.20 2018-10-31 11:01:38 -07:00
scripts Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-12-21 09:22:24 -08:00
security ima: cleanup the match_token policy code 2018-12-17 16:31:28 -08:00
sound ALSA: hda/realtek: Enable audio jacks of ASUS UX433FN/UX333FA with ALC294 2018-12-10 11:25:22 +01:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-19 23:34:33 -08:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: fix unregistering coalesced mmio zone from wrong bus 2018-12-18 22:07:25 +01:00
.clang-format page cache: Convert find_get_pages_contig to XArray 2018-10-21 10:46:34 -04:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.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 mailmap: Update email for Punit Agrawal 2018-11-05 10:02:11 +00:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: update entry for MMP platform 2018-12-03 12:39:57 -08:00
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 git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-21 14:21:17 -08:00
Makefile Linux 4.20 2018-12-23 15:55:59 -08:00
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.