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Compiler Attributes: disable __counted_by for clang < 19.1.3

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This patch disables __counted_by for clang versions < 19.1.3 because
of the two issues listed below. It does this by introducing
CONFIG_CC_HAS_COUNTED_BY.

1. clang < 19.1.2 has a bug that can lead to __bdos returning 0:
https://github.com/llvm/llvm-project/pull/110497

2. clang < 19.1.3 has a bug that can lead to __bdos being off by 4:
https://github.com/llvm/llvm-project/pull/112636

Fixes: c8248faf3c ("Compiler Attributes: counted_by: Adjust name and identifier expansion")
Cc: stable@vger.kernel.org # 6.6.x: 16c31dd7fd: Compiler Attributes: counted_by: bump min gcc version
Cc: stable@vger.kernel.org # 6.6.x: 2993eb7a8d: Compiler Attributes: counted_by: fixup clang URL
Cc: stable@vger.kernel.org # 6.6.x: 231dc3f0c9: lkdtm/bugs: Improve warning message for compilers without counted_by support
Cc: stable@vger.kernel.org # 6.6.x
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/all/20240913164630.GA4091534@thelio-3990X/
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202409260949.a1254989-oliver.sang@intel.com
Link: https://lore.kernel.org/all/Zw8iawAF5W2uzGuh@archlinux/T/#m204c09f63c076586a02d194b87dffc7e81b8de7b
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Jan Hendrik Farr <kernel@jfarr.cc>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://lore.kernel.org/r/20241029140036.577804-2-kernel@jfarr.cc
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Jan Hendrik Farr 2024-10-29 15:00:36 +01:00 committed by Kees Cook
parent d7a516c6ee
commit f06e108a3d
5 changed files with 30 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/misc/lkdtm/bugs.c
View File

@ -445,7 +445,7 @@ static void lkdtm_FAM_BOUNDS(void)
pr_err("FAIL: survived access of invalid flexible array member index!\n");
if (!__has_attribute(__counted_by__))
if (!IS_ENABLED(CONFIG_CC_HAS_COUNTED_BY))
pr_warn("This is expected since this %s was built with a compiler that does not support __counted_by\n",
lkdtm_kernel_info);
else if (IS_ENABLED(CONFIG_UBSAN_BOUNDS))

13
include/linux/compiler_attributes.h
View File

@ -94,19 +94,6 @@
# define __copy(symbol)
#endif
/*
* Optional: only supported since gcc >= 15
* Optional: only supported since clang >= 18
*
* gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
* clang: https://github.com/llvm/llvm-project/pull/76348
*/
#if __has_attribute(__counted_by__)
# define __counted_by(member) __attribute__((__counted_by__(member)))
#else
# define __counted_by(member)
#endif
/*
* Optional: not supported by gcc
* Optional: only supported since clang >= 14.0

19
include/linux/compiler_types.h
View File

@ -323,6 +323,25 @@ struct ftrace_likely_data {
#define __no_sanitize_or_inline __always_inline
#endif
/*
* Optional: only supported since gcc >= 15
* Optional: only supported since clang >= 18
*
* gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
* clang: https://github.com/llvm/llvm-project/pull/76348
*
* __bdos on clang < 19.1.2 can erroneously return 0:
* https://github.com/llvm/llvm-project/pull/110497
*
* __bdos on clang < 19.1.3 can be off by 4:
* https://github.com/llvm/llvm-project/pull/112636
*/
#ifdef CONFIG_CC_HAS_COUNTED_BY
# define __counted_by(member) __attribute__((__counted_by__(member)))
#else
# define __counted_by(member)
#endif
/*
* Apply __counted_by() when the Endianness matches to increase test coverage.
*/

9
init/Kconfig
View File

@ -116,6 +116,15 @@ config CC_HAS_ASM_INLINE
config CC_HAS_NO_PROFILE_FN_ATTR
def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
config CC_HAS_COUNTED_BY
# TODO: when gcc 15 is released remove the build test and add
# a gcc version check
def_bool $(success,echo 'struct flex { int count; int array[] __attribute__((__counted_by__(count))); };' | $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror)
# clang needs to be at least 19.1.3 to avoid __bdos miscalculations
# https://github.com/llvm/llvm-project/pull/110497
# https://github.com/llvm/llvm-project/pull/112636
depends on !(CC_IS_CLANG && CLANG_VERSION < 190103)
config PAHOLE_VERSION
int
default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))

2
lib/overflow_kunit.c
View File

@ -1187,7 +1187,7 @@ static void DEFINE_FLEX_test(struct kunit *test)
{
/* Using _RAW_ on a __counted_by struct will initialize "counter" to zero */
DEFINE_RAW_FLEX(struct foo, two_but_zero, array, 2);
#if __has_attribute(__counted_by__)
#ifdef CONFIG_CC_HAS_COUNTED_BY
int expected_raw_size = sizeof(struct foo);
#else
int expected_raw_size = sizeof(struct foo) + 2 * sizeof(s16);