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Kees Cook db44404d1b randstruct: gcc-plugin: Remove bogus void member 
[ Upstream commit e136a40621 ]

When building the randomized replacement tree of struct members, the
randstruct GCC plugin would insert, as the first member, a 0-sized void
member. This appears as though it was done to catch non-designated
("unnamed") static initializers, which wouldn't be stable since they
depend on the original struct layout order.

This was accomplished by having the side-effect of the "void member"
tripping an assert in GCC internals (count_type_elements) if the member
list ever needed to be counted (e.g. for figuring out the order of members
during a non-designated initialization), which would catch impossible type
(void) in the struct:

security/landlock/fs.c: In function ‘hook_file_ioctl_common’:
security/landlock/fs.c:1745:61: internal compiler error: in count_type_elements, at expr.cc:7075
 1745 |                         .u.op = &(struct lsm_ioctlop_audit) {
      |                                                             ^

static HOST_WIDE_INT
count_type_elements (const_tree type, bool for_ctor_p)
{
  switch (TREE_CODE (type))
...
    case VOID_TYPE:
    default:
      gcc_unreachable ();
    }
}

However this is a redundant safety measure since randstruct uses the
__designated_initializer attribute both internally and within the
__randomized_layout attribute macro so that this would be enforced
by the compiler directly even when randstruct was not enabled (via
-Wdesignated-init).

A recent change in Landlock ended up tripping the same member counting
routine when using a full-struct copy initializer as part of an anonymous
initializer. This, however, is a false positive as the initializer is
copying between identical structs (and hence identical layouts). The
"path" member is "struct path", a randomized struct, and is being copied
to from another "struct path", the "f_path" member:

        landlock_log_denial(landlock_cred(file->f_cred), &(struct landlock_request) {
                .type = LANDLOCK_REQUEST_FS_ACCESS,
                .audit = {
                        .type = LSM_AUDIT_DATA_IOCTL_OP,
                        .u.op = &(struct lsm_ioctlop_audit) {
                                .path = file->f_path,
                                .cmd = cmd,
                        },
                },
	...

As can be seen with the coming randstruct KUnit test, there appears to
be no behavioral problems with this kind of initialization when the void
member is removed from the randstruct GCC plugin, so remove it.

Reported-by: "Dr. David Alan Gilbert" <linux@treblig.org>
Closes: https://lore.kernel.org/lkml/Z_PRaKx7q70MKgCA@gallifrey/
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/lkml/20250407-kbuild-disable-gcc-plugins-v1-1-5d46ae583f5e@kernel.org/
Reported-by: WangYuli <wangyuli@uniontech.com>
Closes: https://lore.kernel.org/lkml/337D5D4887277B27+3c677db3-a8b9-47f0-93a4-7809355f1381@uniontech.com/
Fixes: 313dd1b629 ("gcc-plugins: Add the randstruct plugin")
Signed-off-by: Kees Cook <kees@kernel.org>
Stable-dep-of: f39f18f3c3 ("randstruct: gcc-plugin: Fix attribute addition")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-09-09 18:50:23 +02:00
arch arm64: dts: marvell: uDPU: define pinctrl state for alarm LEDs 2025-09-09 18:50:23 +02:00
block block: avoid possible overflow for chunk_sectors check in blk_stack_limits() 2025-08-28 16:24:25 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: xts - Only add ecb if it is not already there 2025-06-27 11:05:10 +01:00
Documentation asm-generic: Add memory barrier dma_mb() 2025-08-28 16:24:36 +02:00
drivers vmxnet3: update MTU after device quiesce 2025-09-09 18:50:23 +02:00
fs fs: writeback: fix use-after-free in __mark_inode_dirty() 2025-09-09 18:50:17 +02:00
include mm: move page table sync declarations to linux/pgtable.h 2025-09-09 18:50:21 +02:00
init sched/isolation: Make CONFIG_CPU_ISOLATION depend on CONFIG_SMP 2025-05-02 07:44:36 +02:00
io_uring io_uring: fix possible deadlock in io_register_iowq_max_workers() 2024-11-17 15:06:25 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:05:26 +01:00
kernel cpufreq/sched: Explicitly synchronize limits_changed flag handling 2025-09-09 18:50:22 +02:00
lib lib: bitmap: Introduce node-aware alloc API 2025-08-28 16:24:02 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/khugepaged: fix ->anon_vma race 2025-09-09 18:50:22 +02:00
net net: dsa: microchip: linearize skb for tail-tagging switches 2025-09-09 18:50:23 +02:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts randstruct: gcc-plugin: Remove bogus void member 2025-09-09 18:50:23 +02:00
security securityfs: don't pin dentries twice, once is enough... 2025-08-28 16:24:17 +02:00
sound ALSA: usb-audio: Add mute TLV for playback volumes on some devices 2025-09-09 18:50:20 +02:00
tools selftests: mptcp: pm: check flush doesn't reset limits 2025-08-28 16:24:37 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-10-22 15:40:41 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS trace: Relocate event helper files 2024-04-10 16:19:24 +02:00
Makefile Linux 5.15.191 2025-09-04 14:28:48 +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.