linux-stable.git/scripts/gcc-plugins/randomize_layout_plugin.c, branch v5.15.208

randstruct: gcc-plugin: Fix attribute addition

2025-09-09T16:50:23+00:00

[ Upstream commit f39f18f3c3531aa802b58a20d39d96e82eb96c14 ]

Based on changes in the 2021 public version of the randstruct
out-of-tree GCC plugin[1], more carefully update the attributes on
resulting decls, to avoid tripping checks in GCC 15's
comptypes_check_enum_int() when it has been configured with
"--enable-checking=misc":

arch/arm64/kernel/kexec_image.c:132:14: internal compiler error: in comptypes_check_enum_int, at c/c-typeck.cc:1519
  132 | const struct kexec_file_ops kexec_image_ops = {
      |              ^~~~~~~~~~~~~~
 internal_error(char const*, ...), at gcc/gcc/diagnostic-global-context.cc:517
 fancy_abort(char const*, int, char const*), at gcc/gcc/diagnostic.cc:1803
 comptypes_check_enum_int(tree_node*, tree_node*, bool*), at gcc/gcc/c/c-typeck.cc:1519
 ...

Link: https://archive.org/download/grsecurity/grsecurity-3.1-5.10.41-202105280954.patch.gz [1]
Reported-by: Thiago Jung Bauermann 
Closes: https://github.com/KSPP/linux/issues/367
Closes: https://lore.kernel.org/lkml/20250530000646.104457-1-thiago.bauermann@linaro.org/
Reported-by: Ingo Saitz 
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1104745
Fixes: 313dd1b62921 ("gcc-plugins: Add the randstruct plugin")
Tested-by: Thiago Jung Bauermann 
Link: https://lore.kernel.org/r/20250530221824.work.623-kees@kernel.org
Signed-off-by: Kees Cook 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

randstruct: gcc-plugin: Remove bogus void member

2025-09-09T16:50:23+00:00

[ Upstream commit e136a4062174a9a8d1c1447ca040ea81accfa6a8 ]

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" 
Closes: https://lore.kernel.org/lkml/Z_PRaKx7q70MKgCA@gallifrey/
Reported-by: Mark Brown 
Closes: https://lore.kernel.org/lkml/20250407-kbuild-disable-gcc-plugins-v1-1-5d46ae583f5e@kernel.org/
Reported-by: WangYuli 
Closes: https://lore.kernel.org/lkml/337D5D4887277B27+3c677db3-a8b9-47f0-93a4-7809355f1381@uniontech.com/
Fixes: 313dd1b62921 ("gcc-plugins: Add the randstruct plugin")
Signed-off-by: Kees Cook 
Stable-dep-of: f39f18f3c353 ("randstruct: gcc-plugin: Fix attribute addition")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

randstruct: Fix gcc-plugin performance mode to stay in group

2023-11-28T16:56:26+00:00

commit 381fdb73d1e2a48244de7260550e453d1003bb8e upstream.

The performance mode of the gcc-plugin randstruct was shuffling struct
members outside of the cache-line groups. Limit the range to the
specified group indexes.

Cc: linux-hardening@vger.kernel.org
Cc: stable@vger.kernel.org
Reported-by: Lukas Loidolt 
Closes: https://lore.kernel.org/all/f3ca77f0-e414-4065-83a5-ae4c4d25545d@student.tuwien.ac.at
Fixes: 313dd1b62921 ("gcc-plugins: Add the randstruct plugin")
Signed-off-by: Kees Cook 
Signed-off-by: Greg Kroah-Hartman

gcc-plugins: remove code for GCC versions older than 4.9

2020-12-04T22:09:41+00:00

Documentation/process/changes.rst says the minimal GCC version is 4.9.
Hence, BUILDING_GCC_VERSION is greater than or equal to 4009.

Signed-off-by: Masahiro Yamada 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20201202134929.99883-1-masahiroy@kernel.org

randstruct: Check member structs in is_pure_ops_struct()

2019-07-31T20:13:22+00:00

While no uses in the kernel triggered this case, it was possible to have
a false negative where a struct contains other structs which contain only
function pointers because of unreachable code in is_pure_ops_struct().

Signed-off-by: Joonwon Kang 
Link: https://lore.kernel.org/r/20190727155841.GA13586@host
Fixes: 313dd1b62921 ("gcc-plugins: Add the randstruct plugin")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook

security: convert security hooks to use hlist

2018-03-31T02:18:27+00:00

This changes security_hook_heads to use hlist_heads instead of
the circular doubly-linked list heads. This should cut down
the size of the struct by about half.

In addition, it allows mutation of the hooks at the tail of the
callback list without having to modify the head. The longer-term
purpose of this is to enable making the heads read only.

Signed-off-by: Sargun Dhillon 
Reviewed-by: Tetsuo Handa 
Acked-by: Casey Schaufler 
Signed-off-by: James Morris

gcc-plugins: Use dynamic initializers

2018-02-06T01:27:46+00:00

GCC 8 changed the order of some fields and is very picky about ordering
in static initializers, so instead just move to dynamic initializers,
and drop the redundant already-zero field assignments.

Suggested-by: Valdis Kletnieks 
Signed-off-by: Kees Cook

randstruct: Enable function pointer struct detection

2017-08-02T00:04:48+00:00

This enables the automatic structure selection logic in the randstruct
GCC plugin. The selection logic randomizes all structures that contain
only function pointers, unless marked with __no_randomize_layout.

Signed-off-by: Kees Cook

randstruct: Whitelist NIU struct page overloading

2017-06-22T23:21:43+00:00

The NIU ethernet driver intentionally stores a page struct pointer on
top of the "mapping" field. Whitelist this case:

drivers/net/ethernet/sun/niu.c: In function ‘niu_rx_pkt_ignore’:
drivers/net/ethernet/sun/niu.c:3402:10: note: found mismatched ssa struct pointer types: ‘struct page’ and ‘struct address_space’

    *link = (struct page *) page->mapping;
    ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cc: David S. Miller 
Signed-off-by: Kees Cook

randstruct: Whitelist big_key path struct overloading

2017-06-22T23:21:42+00:00

The big_key payload structure intentionally stores a struct path in
two void pointers to avoid header soup. Whitelist this case:

security/keys/big_key.c: In function ‘big_key_read’:
security/keys/big_key.c:293:16: note: found mismatched rhs struct pointer types: ‘struct path’ and ‘void *’

   struct path *path = (struct path *)&key->payload.data[big_key_path];
                ^~~~

Cc: David Howells 
Signed-off-by: Kees Cook