6.12-stable review patch. If anyone has any objections, please let me know.
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From: Jan Hendrik Farr kernel@jfarr.cc
commit f06e108a3dc53c0f5234d18de0bd224753db5019 upstream.
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: c8248faf3ca2 ("Compiler Attributes: counted_by: Adjust name and identifier expansion") Cc: stable@vger.kernel.org # 6.6.x: 16c31dd7fdf6: Compiler Attributes: counted_by: bump min gcc version Cc: stable@vger.kernel.org # 6.6.x: 2993eb7a8d34: Compiler Attributes: counted_by: fixup clang URL Cc: stable@vger.kernel.org # 6.6.x: 231dc3f0c936: 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/#m204c09f63c076586a... 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/misc/lkdtm/bugs.c | 2 +- include/linux/compiler_attributes.h | 13 ------------- include/linux/compiler_types.h | 19 +++++++++++++++++++ init/Kconfig | 9 +++++++++ lib/overflow_kunit.c | 2 +- 5 files changed, 30 insertions(+), 15 deletions(-)
--- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -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)) --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -95,19 +95,6 @@ #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 * --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -324,6 +324,25 @@ struct ftrace_likely_data { #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. */ #ifdef __LITTLE_ENDIAN --- a/init/Kconfig +++ b/init/Kconfig @@ -120,6 +120,15 @@ 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)) --- a/lib/overflow_kunit.c +++ b/lib/overflow_kunit.c @@ -1187,7 +1187,7 @@ static void DEFINE_FLEX_test(struct kuni { /* 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);