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Charles Haithcock 1c72e7b0b4 i2c: i801: Revert "i2c: i801: replace acpi_lock with I2C bus lock" [ Upstream commit `cfc69c2e6c` ] This reverts commit `f707d6b9e7`. Under rare circumstances, multiple udev threads can collect i801 device info on boot and walk i801_acpi_io_handler somewhat concurrently. The first will note the area is reserved by acpi to prevent further touches. This ultimately causes the area to be deregistered. The second will enter i801_acpi_io_handler after the area is unregistered but before a check can be made that the area is unregistered. i2c_lock_bus relies on the now unregistered area containing lock_ops to lock the bus. The end result is a kernel panic on boot with the following backtrace; [ 14.971872] ioatdma 0000:09:00.2: enabling device (0100 -> 0102) [ 14.971873] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 14.971880] #PF: supervisor read access in kernel mode [ 14.971884] #PF: error_code(0x0000) - not-present page [ 14.971887] PGD 0 P4D 0 [ 14.971894] Oops: 0000 [#1] PREEMPT SMP PTI [ 14.971900] CPU: 5 PID: 956 Comm: systemd-udevd Not tainted 5.14.0-611.5.1.el9_7.x86_64 #1 [ 14.971905] Hardware name: XXXXXXXXXXXXXXXXXXXXXXX BIOS 1.20.10.SV91 01/30/2023 [ 14.971908] RIP: 0010:i801_acpi_io_handler+0x2d/0xb0 [i2c_i801] [ 14.971929] Code: 00 00 49 8b 40 20 41 57 41 56 4d 8b b8 30 04 00 00 49 89 ce 41 55 41 89 d5 41 54 49 89 f4 be 02 00 00 00 55 4c 89 c5 53 89 fb <48> 8b 00 4c 89 c7 e8 18 61 54 e9 80 bd 80 04 00 00 00 75 09 4c 3b [ 14.971933] RSP: 0018:ffffbaa841483838 EFLAGS: 00010282 [ 14.971938] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff9685e01ba568 [ 14.971941] RDX: 0000000000000008 RSI: 0000000000000002 RDI: 0000000000000000 [ 14.971944] RBP: ffff9685ca22f028 R08: ffff9685ca22f028 R09: ffff9685ca22f028 [ 14.971948] R10: 000000000000000b R11: 0000000000000580 R12: 0000000000000580 [ 14.971951] R13: 0000000000000008 R14: ffff9685e01ba568 R15: ffff9685c222f000 [ 14.971954] FS: 00007f8287c0ab40(0000) GS:ffff96a47f940000(0000) knlGS:0000000000000000 [ 14.971959] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 14.971963] CR2: 0000000000000000 CR3: 0000000168090001 CR4: 00000000003706f0 [ 14.971966] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 14.971968] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 14.971972] Call Trace: [ 14.971977] <TASK> [ 14.971981] ? show_trace_log_lvl+0x1c4/0x2df [ 14.971994] ? show_trace_log_lvl+0x1c4/0x2df [ 14.972003] ? acpi_ev_address_space_dispatch+0x16e/0x3c0 [ 14.972014] ? __die_body.cold+0x8/0xd [ 14.972021] ? page_fault_oops+0x132/0x170 [ 14.972028] ? exc_page_fault+0x61/0x150 [ 14.972036] ? asm_exc_page_fault+0x22/0x30 [ 14.972045] ? i801_acpi_io_handler+0x2d/0xb0 [i2c_i801] [ 14.972061] acpi_ev_address_space_dispatch+0x16e/0x3c0 [ 14.972069] ? __pfx_i801_acpi_io_handler+0x10/0x10 [i2c_i801] [ 14.972085] acpi_ex_access_region+0x5b/0xd0 [ 14.972093] acpi_ex_field_datum_io+0x73/0x2e0 [ 14.972100] acpi_ex_read_data_from_field+0x8e/0x230 [ 14.972106] acpi_ex_resolve_node_to_value+0x23d/0x310 [ 14.972114] acpi_ds_evaluate_name_path+0xad/0x110 [ 14.972121] acpi_ds_exec_end_op+0x321/0x510 [ 14.972127] acpi_ps_parse_loop+0xf7/0x680 [ 14.972136] acpi_ps_parse_aml+0x17a/0x3d0 [ 14.972143] acpi_ps_execute_method+0x137/0x270 [ 14.972150] acpi_ns_evaluate+0x1f4/0x2e0 [ 14.972158] acpi_evaluate_object+0x134/0x2f0 [ 14.972164] acpi_evaluate_integer+0x50/0xe0 [ 14.972173] ? vsnprintf+0x24b/0x570 [ 14.972181] acpi_ac_get_state.part.0+0x23/0x70 [ 14.972189] get_ac_property+0x4e/0x60 [ 14.972195] power_supply_show_property+0x90/0x1f0 [ 14.972205] add_prop_uevent+0x29/0x90 [ 14.972213] power_supply_uevent+0x109/0x1d0 [ 14.972222] dev_uevent+0x10e/0x2f0 [ 14.972228] uevent_show+0x8e/0x100 [ 14.972236] dev_attr_show+0x19/0x40 [ 14.972246] sysfs_kf_seq_show+0x9b/0x100 [ 14.972253] seq_read_iter+0x120/0x4b0 [ 14.972262] ? selinux_file_permission+0x106/0x150 [ 14.972273] vfs_read+0x24f/0x3a0 [ 14.972284] ksys_read+0x5f/0xe0 [ 14.972291] do_syscall_64+0x5f/0xe0 ... The kernel panic is mitigated by setting limiting the count of udev children to 1. Revert to using the acpi_lock to continue protecting marking the area as owned by firmware without relying on a lock in a potentially unmapped region of memory. Fixes: `f707d6b9e7` ("i2c: i801: replace acpi_lock with I2C bus lock") Signed-off-by: Charles Haithcock <chaithco@redhat.com> [wsa: added Fixes-tag and updated comment stating the importance of the lock] Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		History 2026-03-12 07:09:56 -04:00
arch	ARM: clean up the memset64() C wrapper	2026-03-12 07:09:44 -04:00
block	block: decouple secure erase size limit from discard size limit	2026-03-04 07:19:38 -05:00
certs	sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3	2024-09-20 19:52:48 +03:00
crypto	crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec	2026-01-30 10:32:12 +01:00
Documentation	hwmon: (aht10) Add support for dht20	2026-03-12 07:09:46 -04:00
drivers	i2c: i801: Revert "i2c: i801: replace acpi_lock with I2C bus lock"	2026-03-12 07:09:56 -04:00
fs	smb/client: fix buffer size for smb311_posix_qinfo in SMB311_posix_query_info()	2026-03-12 07:09:56 -04:00
include	net: ipv4: fix ARM64 alignment fault in multipath hash seed	2026-03-12 07:09:56 -04:00
init	printk changes for 6.18	2025-10-04 11:13:11 -07:00
io_uring	io_uring/zcrx: fix user_ref race between scrub and refill paths	2026-03-04 07:21:33 -05:00
ipc	ipc: don't audit capability check in ipc_permissions()	2026-02-26 14:59:19 -08:00
kernel	bpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim	2026-03-12 07:09:55 -04:00
lib	debugobject: Make it work with deferred page initialization - again	2026-03-12 07:09:08 -04:00
LICENSES	LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2	2025-07-24 11:15:39 +02:00
mm	mm: thp: deny THP for files on anonymous inodes	2026-03-12 07:09:41 -04:00
net	net: ipv4: fix ARM64 alignment fault in multipath hash seed	2026-03-12 07:09:56 -04:00
rust	rust: kunit: fix warning when !CONFIG_PRINTK	2026-03-12 07:09:52 -04:00
samples	samples/ftrace: Adjust LoongArch register restore order in direct calls	2026-01-08 10:17:11 +01:00
scripts	kbuild: rpm-pkg: Disable automatic requires for manual debuginfo package	2026-03-04 07:21:32 -05:00
security	ima: verify the previous kernel's IMA buffer lies in addressable RAM	2026-03-04 07:21:17 -05:00
sound	ASoC: fsl_xcvr: provide regmap names	2026-03-12 07:09:44 -04:00
tools	kunit: tool: copy caller args in run_kernel to prevent mutation	2026-03-12 07:09:52 -04:00
usr	gen_init_cpio: Ignore fsync() returning EINVAL on pipes	2025-10-07 09:53:05 -07:00
virt	KVM: Don't clobber irqfd routing type when deassigning irqfd	2026-02-11 13:41:44 +01:00
.clang-format	memblock: drop for_each_free_mem_pfn_range_in_zone_from()	2025-09-14 08:49:03 +03:00
.clippy.toml	rust: clean Rust 1.88.0's warning about `clippy::disallowed_macros` configuration	2025-05-07 00:11:47 +02:00
.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: remove Alyssa Rosenzweig	2025-09-18 21:17:31 +02:00
.gitattributes	.gitattributes: set diff driver for Rust source code files	2023-05-31 17:48:25 +02:00
.gitignore	.gitignore: ignore compile_commands.json globally	2025-08-12 15:53:55 -07:00
.mailmap	8 hotfixes. 4 are cc:stable, 7 are against mm/.	2025-11-26 12:38:05 -08:00
.pylintrc	tools: docs: parse-headers.py: move it from sphinx dir	2025-08-29 15:54:42 -06:00
.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: mark ISDN subsystem as orphan	2025-10-27 17:49:45 -07:00
Kbuild	sched: Make migrate_{en,dis}able() inline	2025-09-25 09:57:16 +02:00
Kconfig	io_uring: Rename KConfig to Kconfig	2025-02-19 14:53:27 -07:00
MAINTAINERS	soc: fixes for 6.18, part 4	2025-11-28 09:57:31 -08:00
Makefile	Linux 6.18.16	2026-03-04 07:25:12 -05:00
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.