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Shakeel Butt e6cc9ff2ac memcg: protect concurrent access to mem_cgroup_idr 
commit 9972605a23 upstream.

Commit 73f576c04b ("mm: memcontrol: fix cgroup creation failure after
many small jobs") decoupled the memcg IDs from the CSS ID space to fix the
cgroup creation failures.  It introduced IDR to maintain the memcg ID
space.  The IDR depends on external synchronization mechanisms for
modifications.  For the mem_cgroup_idr, the idr_alloc() and idr_replace()
happen within css callback and thus are protected through cgroup_mutex
from concurrent modifications.  However idr_remove() for mem_cgroup_idr
was not protected against concurrency and can be run concurrently for
different memcgs when they hit their refcnt to zero.  Fix that.

We have been seeing list_lru based kernel crashes at a low frequency in
our fleet for a long time.  These crashes were in different part of
list_lru code including list_lru_add(), list_lru_del() and reparenting
code.  Upon further inspection, it looked like for a given object (dentry
and inode), the super_block's list_lru didn't have list_lru_one for the
memcg of that object.  The initial suspicions were either the object is
not allocated through kmem_cache_alloc_lru() or somehow
memcg_list_lru_alloc() failed to allocate list_lru_one() for a memcg but
returned success.  No evidence were found for these cases.

Looking more deeply, we started seeing situations where valid memcg's id
is not present in mem_cgroup_idr and in some cases multiple valid memcgs
have same id and mem_cgroup_idr is pointing to one of them.  So, the most
reasonable explanation is that these situations can happen due to race
between multiple idr_remove() calls or race between
idr_alloc()/idr_replace() and idr_remove().  These races are causing
multiple memcgs to acquire the same ID and then offlining of one of them
would cleanup list_lrus on the system for all of them.  Later access from
other memcgs to the list_lru cause crashes due to missing list_lru_one.

Link: https://lkml.kernel.org/r/20240802235822.1830976-1-shakeel.butt@linux.dev
Fixes: 73f576c04b ("mm: memcontrol: fix cgroup creation failure after many small jobs")
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Muchun Song <muchun.song@linux.dev>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ Adapted over commit be740503ed ("mm: memcontrol: fix cannot alloc the
  maximum memcg ID") and 6f0df8e16e ("memcontrol: ensure memcg acquired by id
  is properly set up") both are not in the tree ]
Signed-off-by: Tomas Krcka <krckatom@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-09-12 11:07:53 +02:00
arch x86/mm: Fix PTI for i386 some more 2024-09-12 11:07:53 +02:00
block block: remove the blk_flush_integrity call in blk_integrity_unregister 2024-09-12 11:07:42 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: aead,cipher - zeroize key buffer after use 2024-07-18 13:07:27 +02:00
Documentation hwspinlock: Introduce hwspin_lock_bust() 2024-09-12 11:07:41 +02:00
drivers gpio: rockchip: fix OF node leak in probe() 2024-09-12 11:07:52 +02:00
fs btrfs: fix race between direct IO write and fsync when using same fd 2024-09-12 11:07:53 +02:00
include net: drop bad gso csum_start and offset in virtio_net_hdr 2024-09-12 11:07:53 +02:00
init init/main.c: Fix potential static_command_line memory overflow 2024-04-27 17:05:28 +02:00
io_uring io_uring/io-wq: limit retrying worker initialisation 2024-08-19 05:45:22 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel workqueue: Improve scalability of workqueue watchdog touch 2024-09-12 11:07:52 +02:00
lib lib/generic-radix-tree.c: Fix rare race in __genradix_ptr_alloc() 2024-09-12 11:07:50 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm memcg: protect concurrent access to mem_cgroup_idr 2024-09-12 11:07:53 +02:00
net net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket 2024-09-12 11:07:53 +02:00
samples Add gitignore file for samples/fanotify/ subdirectory 2024-07-27 10:46:16 +02:00
scripts kbuild: Fix '-S -c' in x86 stack protector scripts 2024-08-19 05:45:16 +02:00
security smack: unix sockets: fix accept()ed socket label 2024-09-12 11:07:45 +02:00
sound ASoC: sunxi: sun4i-i2s: fix LRCLK polarity in i2s mode 2024-09-12 11:07:52 +02:00
tools net: change maximum number of UDP segments to 128 2024-09-12 11:07:53 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-10 16:18:34 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.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: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS trace: Relocate event helper files 2024-04-10 16:19:24 +02:00
Makefile Linux 5.15.166 2024-09-04 13:23:42 +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.