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Kuniyuki Iwashima a44ff12573 Revert "tcp: avoid the lookup process failing to get sk in ehash table" 
[ Upstream commit 81b3ade5d2 ]

This reverts commit 3f4ca5fafc.

Commit 3f4ca5fafc ("tcp: avoid the lookup process failing to get sk in
ehash table") reversed the order in how a socket is inserted into ehash
to fix an issue that ehash-lookup could fail when reqsk/full sk/twsk are
swapped.  However, it introduced another lookup failure.

The full socket in ehash is allocated from a slab with SLAB_TYPESAFE_BY_RCU
and does not have SOCK_RCU_FREE, so the socket could be reused even while
it is being referenced on another CPU doing RCU lookup.

Let's say a socket is reused and inserted into the same hash bucket during
lookup.  After the blamed commit, a new socket is inserted at the end of
the list.  If that happens, we will skip sockets placed after the previous
position of the reused socket, resulting in ehash lookup failure.

As described in Documentation/RCU/rculist_nulls.rst, we should insert a
new socket at the head of the list to avoid such an issue.

This issue, the swap-lookup-failure, and another variant reported in [0]
can all be handled properly by adding a locked ehash lookup suggested by
Eric Dumazet [1].

However, this issue could occur for every packet, thus more likely than
the other two races, so let's revert the change for now.

Link: https://lore.kernel.org/netdev/20230606064306.9192-1-duanmuquan@baidu.com/ [0]
Link: https://lore.kernel.org/netdev/CANn89iK8snOz8TYOhhwfimC7ykYA78GA3Nyv8x06SZYa1nKdyA@mail.gmail.com/ [1]
Fixes: 3f4ca5fafc ("tcp: avoid the lookup process failing to get sk in ehash table")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230717215918.15723-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-07-27 08:50:45 +02:00
arch bpf, arm64: Fix BTI type used for freplace attached functions 2023-07-27 08:50:44 +02:00
block blk-crypto: use dynamic lock class for blk_crypto_profile::lock 2023-07-23 13:49:21 +02:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: jitter - correct health test during initialization 2023-07-19 16:21:42 +02:00
Documentation sched/psi: Allow unprivileged polling of N*2s period 2023-07-27 08:50:38 +02:00
drivers igc: Prevent garbled TX queue with XDP ZEROCOPY 2023-07-27 08:50:44 +02:00
fs cifs: fix mid leak during reconnection after timeout threshold 2023-07-27 08:50:40 +02:00
include net: ipv4: use consistent txhash in TIME_WAIT and SYN_RECV 2023-07-27 08:50:44 +02:00
init gcc: disable '-Warray-bounds' for gcc-13 too 2023-04-26 14:28:43 +02:00
io_uring io_uring: treat -EAGAIN for REQ_F_NOWAIT as final for io-wq 2023-07-27 08:50:23 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf: Repeat check_max_stack_depth for async callbacks 2023-07-27 08:50:44 +02:00
lib maple_tree: set the node limit when creating a new root node 2023-07-27 08:50:24 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm kasan: add kasan_tag_mismatch prototype 2023-07-23 13:49:32 +02:00
net Revert "tcp: avoid the lookup process failing to get sk in ehash table" 2023-07-27 08:50:45 +02:00
rust rust: kernel: Mark rust_fmt_argument as extern "C" 2023-04-26 14:28:38 +02:00
samples samples: ftrace: Save required argument registers in sample trampolines 2023-07-23 13:49:44 +02:00
scripts kallsyms: strip LTO-only suffixes from promoted global functions 2023-07-27 08:50:39 +02:00
security security: keys: Modify mismatched function name 2023-07-27 08:50:43 +02:00
sound ASoC: SOF: ipc3-dtrace: uninitialized data in dfsentry_trace_filter_write() 2023-07-27 08:50:40 +02:00
tools perf build: Fix library not found error when using CSLIBS 2023-07-27 08:50:39 +02:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Avoid illegal stage2 mapping on invalid memory slot 2023-06-28 11:12:23 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS smb: move client and server files to common directory fs/smb 2023-06-28 11:12:40 +02:00
Makefile Linux 6.1.41 2023-07-24 18:55:35 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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.