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Masahiro Yamada c4f7f31b3a Revert "[PATCH] uml: export symbols added by GCC hardened" 
[ Upstream commit 8635e8df47 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-08-23 17:32:29 +02:00
arch Revert "[PATCH] uml: export symbols added by GCC hardened" 2023-08-23 17:32:29 +02:00
block blk-mq: Fix stall due to recursive flush plug 2023-08-03 10:25:41 +02:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto crypto: jitter - correct health test during initialization 2023-07-19 16:36:19 +02:00
Documentation iommu/amd: Introduce Disable IRTE Caching Support 2023-08-23 17:32:27 +02:00
drivers HID: intel-ish-hid: ipc: Add Arrow Lake PCI device ID 2023-08-23 17:32:29 +02:00
fs crypto, cifs: fix error handling in extract_iter_to_sg() 2023-08-23 17:32:23 +02:00
include iopoll: Call cpu_relax() in busy loops 2023-08-23 17:32:26 +02:00
init init, x86: Move mem_encrypt_init() into arch_cpu_finalize_init() 2023-08-08 20:04:49 +02:00
io_uring io_uring: correct check for O_TMPFILE 2023-08-16 18:32:19 +02:00
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 dma-remap: use kvmalloc_array/kvfree for larger dma memory remap 2023-08-23 17:32:27 +02:00
lib debugobjects: Recheck debug_objects_enabled before reporting 2023-08-11 12:14:25 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: memory-failure: avoid false hwpoison page mapped error info 2023-08-16 18:32:20 +02:00
net nexthop: Fix infinite nexthop bucket dump when using maximum nexthop ID 2023-08-16 18:32:28 +02:00
rust rust: allocator: Prevent mis-aligned allocation 2023-08-11 12:14:18 +02:00
samples samples: ftrace: Save required argument registers in sample trampolines 2023-07-23 13:54:09 +02:00
scripts kbuild: rust: avoid creating temporary files 2023-07-27 08:57:06 +02:00
security security: keys: Modify mismatched function name 2023-07-27 08:56:59 +02:00
sound ASoC: SOF: core: Free the firmware trace before calling snd_sof_shutdown() 2023-08-23 17:32:29 +02:00
tools nexthop: Fix infinite nexthop bucket dump when using maximum nexthop ID 2023-08-16 18:32:28 +02:00
usr initramfs: Check negative timestamp to prevent broken cpio archive 2023-04-16 17:37:01 +09:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:26:01 +02:00
.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 mailmap: add entries for Ben Dooks 2023-06-19 13:19:35 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS MAINTAINERS: sctp: move Neil to CREDITS 2023-05-12 08:51:32 +01:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
MAINTAINERS Networking fixes for 6.4-rc8, including fixes from ipsec, bpf, 2023-06-22 17:59:51 -07:00
Makefile Linux 6.4.11 2023-08-16 18:32:31 +02:00
README

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.