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Abel Wu c78f4afbd9 bpf: Fix deadlock when freeing cgroup storage 
The following commit
bc235cdb42 ("bpf: Prevent deadlock from recursive bpf_task_storage_[get|delete]")
first introduced deadlock prevention for fentry/fexit programs attaching
on bpf_task_storage helpers. That commit also employed the logic in map
free path in its v6 version.

Later bpf_cgrp_storage was first introduced in
c4bcfb38a9 ("bpf: Implement cgroup storage available to non-cgroup-attached bpf progs")
which faces the same issue as bpf_task_storage, instead of its busy
counter, NULL was passed to bpf_local_storage_map_free() which opened
a window to cause deadlock:

	<TASK>
		(acquiring local_storage->lock)
	_raw_spin_lock_irqsave+0x3d/0x50
	bpf_local_storage_update+0xd1/0x460
	bpf_cgrp_storage_get+0x109/0x130
	bpf_prog_a4d4a370ba857314_cgrp_ptr+0x139/0x170
	? __bpf_prog_enter_recur+0x16/0x80
	bpf_trampoline_6442485186+0x43/0xa4
	cgroup_storage_ptr+0x9/0x20
		(holding local_storage->lock)
	bpf_selem_unlink_storage_nolock.constprop.0+0x135/0x160
	bpf_selem_unlink_storage+0x6f/0x110
	bpf_local_storage_map_free+0xa2/0x110
	bpf_map_free_deferred+0x5b/0x90
	process_one_work+0x17c/0x390
	worker_thread+0x251/0x360
	kthread+0xd2/0x100
	ret_from_fork+0x34/0x50
	ret_from_fork_asm+0x1a/0x30
	</TASK>

Progs:
 - A: SEC("fentry/cgroup_storage_ptr")
   - cgid (BPF_MAP_TYPE_HASH)
	Record the id of the cgroup the current task belonging
	to in this hash map, using the address of the cgroup
	as the map key.
   - cgrpa (BPF_MAP_TYPE_CGRP_STORAGE)
	If current task is a kworker, lookup the above hash
	map using function parameter @owner as the key to get
	its corresponding cgroup id which is then used to get
	a trusted pointer to the cgroup through
	bpf_cgroup_from_id(). This trusted pointer can then
	be passed to bpf_cgrp_storage_get() to finally trigger
	the deadlock issue.
 - B: SEC("tp_btf/sys_enter")
   - cgrpb (BPF_MAP_TYPE_CGRP_STORAGE)
	The only purpose of this prog is to fill Prog A's
	hash map by calling bpf_cgrp_storage_get() for as
	many userspace tasks as possible.

Steps to reproduce:
 - Run A;
 - while (true) { Run B; Destroy B; }

Fix this issue by passing its busy counter to the free procedure so
it can be properly incremented before storage/smap locking.

Fixes: c4bcfb38a9 ("bpf: Implement cgroup storage available to non-cgroup-attached bpf progs")
Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20241221061018.37717-1-wuyun.abel@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-01-29 18:38:19 -08:00
arch Fix a build regression on certain config and build environment 2025-01-28 14:32:03 -08:00
block Driver core and debugfs updates 2025-01-28 12:25:12 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This update includes the following changes: 2025-01-24 07:48:10 -08:00
Documentation strparser: Add read_sock callback 2025-01-29 13:32:08 -08:00
drivers VFIO updates for v6.14-rc1 2025-01-28 14:16:46 -08:00
fs NFS Client Updates for Linux 6.14 2025-01-28 14:23:46 -08:00
include bpf: Fix wrong copied_seq calculation 2025-01-29 13:32:23 -08:00
init drm merge window fixes part 1 2025-01-27 17:17:16 -08:00
io_uring The various patchsets are summarized below. Plus of course many 2025-01-26 18:36:23 -08:00
ipc ipc/util.c: complete the kernel-doc function descriptions 2025-01-24 22:47:27 -08:00
kernel bpf: Fix deadlock when freeing cgroup storage 2025-01-29 18:38:19 -08:00
lib Driver core and debugfs updates 2025-01-28 12:25:12 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm Driver core and debugfs updates 2025-01-28 12:25:12 -08:00
net bpf: Disable non stream socket for strparser 2025-01-29 13:32:32 -08:00
rust Driver core and debugfs updates 2025-01-28 12:25:12 -08:00
samples Driver core and debugfs updates 2025-01-28 12:25:12 -08:00
scripts Char/Misc/IIO driver updates for 6.14-rc1 2025-01-27 16:51:51 -08:00
security Mainly individually changelogged singleton patches. The patch series in 2025-01-26 17:50:53 -08:00
sound Driver core and debugfs updates 2025-01-28 12:25:12 -08:00
tools selftests/bpf: Add strparser test for bpf 2025-01-29 13:32:48 -08:00
usr kbuild: Drop support for include/asm-<arch> in headers_check.pl 2024-12-21 11:43:17 +09:00
virt Merge branch 'kvm-mirror-page-tables' into HEAD 2025-01-20 07:15:58 -05:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-01-10 00:17:25 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: use host dylib naming convention to support macOS 2025-01-10 01:01:24 +01:00
.mailmap Mainly individually changelogged singleton patches. The patch series in 2025-01-26 17:50:53 -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 Mainly individually changelogged singleton patches. The patch series in 2025-01-26 17:50:53 -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 Driver core and debugfs updates 2025-01-28 12:25:12 -08:00
Makefile Networking changes for 6.14. 2025-01-22 08:28:57 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.