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Marco Elver 706ae66574 kcsan: Avoid READ_ONCE() in read_instrumented_memory() 
commit 8dec88070d upstream.

Haibo Li reported:

 | Unable to handle kernel paging request at virtual address
 |   ffffff802a0d8d7171
 | Mem abort info⭕
 |   ESR = 0x9600002121
 |   EC = 0x25: DABT (current EL), IL = 32 bitsts
 |   SET = 0, FnV = 0 0
 |   EA = 0, S1PTW = 0 0
 |   FSC = 0x21: alignment fault
 | Data abort info⭕
 |   ISV = 0, ISS = 0x0000002121
 |   CM = 0, WnR = 0 0
 | swapper pgtable: 4k pages, 39-bit VAs, pgdp=000000002835200000
 | [ffffff802a0d8d71] pgd=180000005fbf9003, p4d=180000005fbf9003,
 | pud=180000005fbf9003, pmd=180000005fbe8003, pte=006800002a0d8707
 | Internal error: Oops: 96000021 [#1] PREEMPT SMP
 | Modules linked in:
 | CPU: 2 PID: 45 Comm: kworker/u8:2 Not tainted
 |   5.15.78-android13-8-g63561175bbda-dirty #1
 | ...
 | pc : kcsan_setup_watchpoint+0x26c/0x6bc
 | lr : kcsan_setup_watchpoint+0x88/0x6bc
 | sp : ffffffc00ab4b7f0
 | x29: ffffffc00ab4b800 x28: ffffff80294fe588 x27: 0000000000000001
 | x26: 0000000000000019 x25: 0000000000000001 x24: ffffff80294fdb80
 | x23: 0000000000000000 x22: ffffffc00a70fb68 x21: ffffff802a0d8d71
 | x20: 0000000000000002 x19: 0000000000000000 x18: ffffffc00a9bd060
 | x17: 0000000000000001 x16: 0000000000000000 x15: ffffffc00a59f000
 | x14: 0000000000000001 x13: 0000000000000000 x12: ffffffc00a70faa0
 | x11: 00000000aaaaaaab x10: 0000000000000054 x9 : ffffffc00839adf8
 | x8 : ffffffc009b4cf00 x7 : 0000000000000000 x6 : 0000000000000007
 | x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffffffc00a70fb70
 | x2 : 0005ff802a0d8d71 x1 : 0000000000000000 x0 : 0000000000000000
 | Call trace:
 |  kcsan_setup_watchpoint+0x26c/0x6bc
 |  __tsan_read2+0x1f0/0x234
 |  inflate_fast+0x498/0x750
 |  zlib_inflate+0x1304/0x2384
 |  __gunzip+0x3a0/0x45c
 |  gunzip+0x20/0x30
 |  unpack_to_rootfs+0x2a8/0x3fc
 |  do_populate_rootfs+0xe8/0x11c
 |  async_run_entry_fn+0x58/0x1bc
 |  process_one_work+0x3ec/0x738
 |  worker_thread+0x4c4/0x838
 |  kthread+0x20c/0x258
 |  ret_from_fork+0x10/0x20
 | Code: b8bfc2a8 2a0803f7 14000007 d503249f (78bfc2a8) )
 | ---[ end trace 613a943cb0a572b6 ]-----

The reason for this is that on certain arm64 configuration since
e35123d83e ("arm64: lto: Strengthen READ_ONCE() to acquire when
CONFIG_LTO=y"), READ_ONCE() may be promoted to a full atomic acquire
instruction which cannot be used on unaligned addresses.

Fix it by avoiding READ_ONCE() in read_instrumented_memory(), and simply
forcing the compiler to do the required access by casting to the
appropriate volatile type. In terms of generated code this currently
only affects architectures that do not use the default READ_ONCE()
implementation.

The only downside is that we are not guaranteed atomicity of the access
itself, although on most architectures a plain load up to machine word
size should still be atomic (a fact the default READ_ONCE() still relies
on itself).

Reported-by: Haibo Li <haibo.li@mediatek.com>
Tested-by: Haibo Li <haibo.li@mediatek.com>
Cc: <stable@vger.kernel.org> # 5.17+
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-05-11 23:03:40 +09:00
arch parisc: Ensure page alignment in flush functions 2023-05-11 23:03:38 +09:00
block blk-mq: don't plug for head insertions in blk_execute_rq_nowait 2023-05-11 23:03:22 +09:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: drbg - Only fail when jent is unavailable in FIPS mode 2023-05-11 23:03:21 +09:00
Documentation ASoC: dt-bindings: qcom,lpass-rx-macro: correct minItems for clocks 2023-05-11 23:03:05 +09:00
drivers mailbox: zynqmp: Fix IPI isr handling 2023-05-11 23:03:40 +09:00
fs nilfs2: fix infinite loop in nilfs_mdt_get_block() 2023-05-11 23:03:39 +09:00
include SUNRPC: remove the maximum number of retries in call_bind_status 2023-05-11 23:03:35 +09:00
init gcc: disable '-Warray-bounds' for gcc-13 too 2023-04-26 14:28:43 +02:00
io_uring io_uring/rsrc: use nospec'ed indexes 2023-05-11 23:03:24 +09:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel kcsan: Avoid READ_ONCE() in read_instrumented_memory() 2023-05-11 23:03:40 +09:00
lib debugobject: Prevent init race with static objects 2023-05-11 23:03:16 +09:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm kasan: hw_tags: avoid invalid virt_to_page() 2023-05-11 23:03:39 +09:00
net SUNRPC: remove the maximum number of retries in call_bind_status 2023-05-11 23:03:35 +09:00
rust rust: kernel: Mark rust_fmt_argument as extern "C" 2023-04-26 14:28:38 +02:00
samples ftrace: Export ftrace_free_filter() to modules 2023-02-01 08:34:37 +01:00
scripts scripts/gdb: raise error with reduced debugging information 2023-05-11 23:03:30 +09:00
security selinux: ensure av_permissions.h is built when needed 2023-05-11 23:03:06 +09:00
sound ALSA: hda/realtek: Fix mute and micmute LEDs for an HP laptop 2023-05-11 23:03:39 +09:00
tools tracing/user_events: Ensure write index cannot be negative 2023-05-11 23:03:32 +09:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Register /dev/kvm as the _very_ last thing during initialization 2023-03-10 09:34:11 +01:00
.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 audit: update the mailing list in MAINTAINERS 2023-02-25 11:25:42 +01:00
Makefile Linux 6.1.27 2023-05-01 08:26:28 +09:00
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.