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Hou Tao 89d92e4fc5 bpf: Check map->usercnt after timer->timer is assigned [ Upstream commit `fd381ce60a` ] When there are concurrent uref release and bpf timer init operations, the following sequence diagram is possible. It will break the guarantee provided by bpf_timer: bpf_timer will still be alive after userspace application releases or unpins the map. It also will lead to kmemleak for old kernel version which doesn't release bpf_timer when map is released. bpf program X: bpf_timer_init() lock timer->lock read timer->timer as NULL read map->usercnt != 0 process Y: close(map_fd) // put last uref bpf_map_put_uref() atomic_dec_and_test(map->usercnt) array_map_free_timers() bpf_timer_cancel_and_free() // just return read timer->timer is NULL t = bpf_map_kmalloc_node() timer->timer = t unlock timer->lock Fix the problem by checking map->usercnt after timer->timer is assigned, so when there are concurrent uref release and bpf timer init, either bpf_timer_cancel_and_free() from uref release reads a no-NULL timer or the newly-added atomic64_read() returns a zero usercnt. Because atomic_dec_and_test(map->usercnt) and READ_ONCE(timer->timer) in bpf_timer_cancel_and_free() are not protected by a lock, so add a memory barrier to guarantee the order between map->usercnt and timer->timer. Also use WRITE_ONCE(timer->timer, x) to match the lockless read of timer->timer in bpf_timer_cancel_and_free(). Reported-by: Hsin-Wei Hung <hsinweih@uci.edu> Closes: https://lore.kernel.org/bpf/CABcoxUaT2k9hWsS1tNgXyoU3E-=PuOgMn737qK984fbFmfYixQ@mail.gmail.com Fixes: `b00628b1c7` ("bpf: Introduce bpf timers.") Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20231030063616.1653024-1-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		History 2023-11-20 11:52:15 +01:00
arch	x86/sev: Change snp_guest_issue_request()'s fw_err argument	2023-11-20 11:52:13 +01:00
block	blk-throttle: check for overflow in calculate_bytes_allowed	2023-11-02 09:35:29 +01:00
certs	certs: Fix build error when PKCS#11 URI contains semicolon	2023-02-09 11:28:11 +01:00
crypto	crypto: lrw,xts - Replace strlcpy with strscpy	2023-09-23 11:11:01 +02:00
Documentation	x86/sev: Change snp_guest_issue_request()'s fw_err argument	2023-11-20 11:52:13 +01:00
drivers	watchdog: ixp4xx: Make sure restart always works	2023-11-20 11:52:15 +01:00
fs	f2fs: fix to initialize map.m_pblk in f2fs_precache_extents()	2023-11-20 11:52:10 +01:00
include	x86/sev: Change snp_guest_issue_request()'s fw_err argument	2023-11-20 11:52:13 +01:00
init	sched/psi: Select KERNFS as needed	2023-09-13 09:42:28 +02:00
io_uring	io_uring/kbuf: Allow the full buffer id space for provided buffers	2023-11-20 11:52:00 +01:00
ipc	ipc: fix memory leak in init_mqueue_fs()	2022-12-31 13:32:01 +01:00
kernel	bpf: Check map->usercnt after timer->timer is assigned	2023-11-20 11:52:15 +01:00
lib	kunit: Fix missed memory release in kunit_free_suite_set()	2023-11-20 11:52:02 +01:00
LICENSES	LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers	2021-12-16 14:33:10 +01:00
mm	filemap: add filemap_get_folios_tag()	2023-11-20 11:52:09 +01:00
net	tipc: Change nla_policy for bearer-related names to NLA_NUL_STRING	2023-11-20 11:52:15 +01:00
rust	rust: allocator: Prevent mis-aligned allocation	2023-08-11 12:08:18 +02:00
samples	fprobe: Pass entry_data to handlers	2023-10-25 12:03:12 +02:00
scripts	modpost: fix ishtp MODULE_DEVICE_TABLE built on big-endian host	2023-11-20 11:52:12 +01:00
security	apparmor: fix invalid reference on profile->disconnected	2023-11-20 11:52:09 +01:00
sound	ASoC: ams-delta.c: use component after check	2023-11-20 11:52:08 +01:00
tools	perf hist: Add missing puts to hist__account_cycles	2023-11-20 11:52:12 +01:00
usr	usr/gen_init_cpio.c: remove unnecessary -1 values from int file	2022-10-03 14:21:44 -07:00
virt	kvm/vfio: ensure kvg instance stays around in kvm_vfio_group_add()	2023-09-13 09:42:46 +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	devlink: move code to a dedicated directory	2023-08-30 16:11:00 +02:00
Makefile	Linux 6.1.62	2023-11-08 14:11:05 +01:00
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.