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Nathan Chancellor 093d9b240a percpu: Fix self-assignment of __old in raw_cpu_generic_try_cmpxchg() 
After commit c5c0ba953b ("percpu: Add {raw,this}_cpu_try_cmpxchg()"),
clang built ARCH=arm and ARCH=arm64 kernels with CONFIG_INIT_STACK_NONE
started panicking on boot in alloc_vmap_area():

  [    0.000000] kernel BUG at mm/vmalloc.c:1638!
  [    0.000000] Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
  [    0.000000] Modules linked in:
  [    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.0-rc2-ARCH+ #1
  [    0.000000] Hardware name: linux,dummy-virt (DT)
  [    0.000000] pstate: 200000c9 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  [    0.000000] pc : alloc_vmap_area+0x7ec/0x7f8
  [    0.000000] lr : alloc_vmap_area+0x7e8/0x7f8

Compiling mm/vmalloc.c with W=2 reveals an instance of -Wshadow, which
helps uncover that through macro expansion, '__old = *(ovalp)' in
raw_cpu_generic_try_cmpxchg() can become '__old = *(&__old)' through
raw_cpu_generic_cmpxchg(), which results in garbage being assigned to
the inner __old and the cmpxchg not working properly.

Add an extra underscore to __old in raw_cpu_generic_try_cmpxchg() so
that there is no more self-assignment, which resolves the panics.

Closes: https://github.com/ClangBuiltLinux/linux/issues/1868
Fixes: c5c0ba953b ("percpu: Add {raw,this}_cpu_try_cmpxchg()")
Debugged-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230607-fix-shadowing-in-raw_cpu_generic_try_cmpxchg-v1-1-8f0a3d930d43@kernel.org
2023-06-08 10:28:39 +02:00
arch locking/atomic: treewide: delete arch_atomic_*() kerneldoc 2023-06-05 09:57:24 +02:00
block for-6.4/block-2023-05-06 2023-05-06 08:28:58 -07:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto This push fixes the following problems: 2023-05-07 10:57:14 -07:00
Documentation locking/atomic: docs: Add atomic operations to the driver basic API documentation 2023-06-05 09:57:24 +02:00
drivers x86,intel_iommu: Replace cmpxchg_double() 2023-06-05 09:36:38 +02:00
fs Some ext4 bug fixes (mostly to address Syzbot reports) for v6.4-rc2. 2023-05-13 17:45:39 -07:00
include percpu: Fix self-assignment of __old in raw_cpu_generic_try_cmpxchg() 2023-06-08 10:28:39 +02:00
init Objtool changes for v6.4: 2023-04-28 14:02:54 -07:00
io_uring for-6.4/io_uring-2023-05-07 2023-05-07 10:00:09 -07:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel locking/atomic: treewide: use raw_atomic*_<op>() 2023-06-05 09:57:20 +02:00
lib types: Introduce [us]128 2023-06-05 09:36:35 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm slub: Replace cmpxchg_double() 2023-06-05 09:36:39 +02:00
net netfilter pull request 23-05-10 2023-05-10 19:08:58 -07:00
rust Rust changes for v6.4 2023-04-30 11:20:22 -07:00
samples LoongArch changes for v6.4 2023-05-04 12:40:16 -07:00
scripts locking/atomic: scripts: generate kerneldoc comments 2023-06-05 09:57:23 +02:00
security integrity-v6.4 2023-04-29 10:11:32 -07:00
sound sound fixes for 6.4-rc1 2023-05-06 08:07:11 -07:00
tools cxl fixes for v6.4-rc2 2023-05-14 12:32:34 -07:00
usr initramfs: Check negative timestamp to prevent broken cpio archive 2023-04-16 17:37:01 +09:00
virt s390: 2023-05-01 12:06:20 -07:00
.clang-format cxl for v6.4 2023-04-30 11:51:51 -07:00
.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 *.dtso files 2023-02-26 15:28:23 +09:00
.gitignore linux-kselftest-kunit-6.4-rc1 2023-04-24 12:31:32 -07:00
.mailmap for-6.4/block-2023-05-06 2023-05-06 08:28:58 -07:00
.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 A handful of late-arriving documentation fixes, plus one Spanish 2023-05-05 13:16:42 -07:00
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 Devicetree binding fixes for v6.4 2023-05-11 09:01:40 -05:00
Makefile Linux 6.4-rc2 2023-05-14 12:51:40 -07:00
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.