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Johannes Weiner b0fdabc908 mm: zswap: fix shrinker NULL crash with cgroup_disable=memory
commit 682886ec69 upstream.

Christian reports a NULL deref in zswap that he bisected down to the zswap
shrinker.  The issue also cropped up in the bug trackers of libguestfs [1]
and the Red Hat bugzilla [2].

The problem is that when memcg is disabled with the boot time flag, the
zswap shrinker might get called with sc->memcg == NULL.  This is okay in
many places, like the lruvec operations.  But it crashes in
memcg_page_state() - which is only used due to the non-node accounting of
cgroup's the zswap memory to begin with.

Nhat spotted that the memcg can be NULL in the memcg-disabled case, and I
was then able to reproduce the crash locally as well.

[1] https://github.com/libguestfs/libguestfs/issues/139
[2] https://bugzilla.redhat.com/show_bug.cgi?id=2275252

Link: https://lkml.kernel.org/r/20240418124043.GC1055428@cmpxchg.org
Link: https://lkml.kernel.org/r/20240417143324.GA1055428@cmpxchg.org
Fixes: b5ba474f3f ("zswap: shrink zswap pool based on memory pressure")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Christian Heusel <christian@heusel.eu>
Debugged-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Christian Heusel <christian@heusel.eu>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Richard W.M. Jones <rjones@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: <stable@vger.kernel.org>	[v6.8]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-05-02 16:35:32 +02:00
Documentation net: make SK_MEMORY_PCPU_RESERV tunable 2024-05-02 16:35:17 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
arch arm64: dts: rockchip: enable internal pull-up for Q7_THRM# on RK3399 Puma 2024-05-02 16:35:28 +02:00
block block: fix module reference leakage from bdev_open_by_dev error path 2024-05-02 16:35:13 +02:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto Revert "crypto: pkcs7 - remove sha1 support" 2024-04-03 15:32:31 +02:00
drivers phy: qcom: qmp-combo: Fix VCO div offset on v3 2024-05-02 16:35:31 +02:00
fs btrfs: fix information leak in btrfs_ioctl_logical_to_ino() 2024-05-02 16:35:27 +02:00
include mm: turn folio_test_hugetlb into a PageType 2024-05-02 16:35:32 +02:00
init rust: make mutually exclusive with CFI_CLANG 2024-05-02 16:35:25 +02:00
io_uring io_uring: Fix io_cqring_wait() not restoring sigmask on get_timespec64() failure 2024-04-27 17:12:47 +02:00
ipc shm: Slim down dependencies 2023-12-20 19:26:31 -05:00
kernel mm: turn folio_test_hugetlb into a PageType 2024-05-02 16:35:32 +02:00
lib stackdepot: respect __GFP_NOLOCKDEP allocation flag 2024-05-02 16:35:31 +02:00
mm mm: zswap: fix shrinker NULL crash with cgroup_disable=memory 2024-05-02 16:35:32 +02:00
net udp: preserve the connected status if only UDP cmsg 2024-05-02 16:35:31 +02:00
rust rust: remove `params` from `module` macro example 2024-05-02 16:35:25 +02:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-09 15:57:48 -08:00
scripts kbuild: rust: force `alloc` extern to allow "empty" Rust files 2024-05-02 16:35:25 +02:00
security selinux: avoid dereference of garbage after mount failure 2024-04-10 16:38:01 +02:00
sound ALSA: hda/realtek - Enable audio jacks of Haier Boyue G42 with ALC269VC 2024-04-27 17:12:57 +02:00
tools selftests/seccomp: Handle EINVAL on unshare(CLONE_NEWPID) 2024-05-02 16:35:24 +02:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-03 15:32:03 +02:00
.clang-format clang-format: Update with v6.7-rc4's `for_each` macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.mailmap drm fixes for 6.8 final 2024-03-08 12:44:56 -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: supplement of zswap maintainers update 2024-01-25 23:52:21 -08:00
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 drm fixes for 6.8 final 2024-03-08 12:44:56 -08:00
Makefile Linux 6.8.8 2024-04-27 17:13:05 +02:00
README

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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    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
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the problems which may result by upgrading your kernel.