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Masahiro Yamada 8635e8df47 Revert "[PATCH] uml: export symbols added by GCC hardened" 
This reverts commit cead61a671.

It exported __stack_smash_handler and __guard, while they may not be
defined by anyone.

The code *declares* __stack_smash_handler and __guard. It does not
create weak symbols. If no external library is linked, they are left
undefined, but yet exported.

If a loadable module tries to access non-existing symbols, bad things
(a page fault, NULL pointer dereference, etc.) will happen. So, the
current code is wrong and dangerous.

If the code were written as follows, it would *define* them as weak
symbols so modules would be able to get access to them.

  void (*__stack_smash_handler)(void *) __attribute__((weak));
  EXPORT_SYMBOL(__stack_smash_handler);

  long __guard __attribute__((weak));
  EXPORT_SYMBOL(__guard);

In fact, modpost forbids exporting undefined symbols. It shows an error
message if it detects such a mistake.

  ERROR: modpost: "..." [...] was exported without definition

Unfortunately, it is checked only when the code is built as modular.
The problem described above has been unnoticed for a long time because
arch/um/os-Linux/user_syms.c is always built-in.

With a planned change in Kbuild, exporting undefined symbols will always
result in a build error instead of a run-time error. It is a good thing,
but we need to fix the breakage in advance.

One fix is to define weak symbols as shown above. An alternative is to
export them conditionally as follows:

  #ifdef CONFIG_STACKPROTECTOR
  extern void __stack_smash_handler(void *);
  EXPORT_SYMBOL(__stack_smash_handler);

  external long __guard;
  EXPORT_SYMBOL(__guard);
  #endif

This is what other architectures do; EXPORT_SYMBOL(__stack_chk_guard)
is guarded by #ifdef CONFIG_STACKPROTECTOR.

However, adding the #ifdef guard is not sensible because UML cannot
enable the stack-protector in the first place! (Please note UML does
not select HAVE_STACKPROTECTOR in Kconfig.)

So, the code is already broken (and unused) in multiple ways.

Just remove.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2023-06-15 04:47:04 +09:00
arch Revert "[PATCH] uml: export symbols added by GCC hardened" 2023-06-15 04:47:04 +09:00
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 kernel-doc: don't let V=1 change outcome 2023-06-10 16:39:02 +09:00
drivers cxl fixes for v6.4-rc2 2023-05-14 12:32:34 -07:00
fs Some ext4 bug fixes (mostly to address Syzbot reports) for v6.4-rc2. 2023-05-13 17:45:39 -07:00
include - Add the required PCI IDs so that the generic SMN accesses provided by 2023-05-14 07:44:48 -07:00
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 Revert "kheaders: substituting --sort in archive creation" 2023-05-28 16:20:21 +09:00
lib Networking fixes for 6.4-rc2, including fixes from netfilter 2023-05-11 08:42:47 -05:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm Reinstate the dmapool changes which were accidentally removed by 2023-05-06 11:43:08 -07:00
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 kbuild: enable kernel-doc -Wall for W=2 2023-06-10 16:39:27 +09:00
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: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +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
.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.