* Re: [PATCH 1/1] Compiler Attributes: disable __counted_by for clang < 19.1.3
2024-10-29 14:00 ` [PATCH 1/1] Compiler Attributes: " Jan Hendrik Farr
@ 2024-10-29 15:10 ` Thorsten Blum
2024-11-19 17:26 ` Kees Cook
2025-06-09 13:14 ` Dafna Hirschfeld
2 siblings, 0 replies; 6+ messages in thread
From: Thorsten Blum @ 2024-10-29 15:10 UTC (permalink / raw)
To: Jan Hendrik Farr
Cc: kees, nathan, ojeda, ndesaulniers, morbo, justinstitt, ardb,
oliver.sang, gustavoars, kent.overstreet, arnd, gregkh, akpm,
tavianator, linux-hardening, llvm, linux-kernel, stable
On 29. Oct 2024, at 15:00, Jan Hendrik Farr wrote:
>
> 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/#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>
Thanks for fixing this and your work on the Clang issues. Feel free to add:
Reviewed-by: Thorsten Blum <thorsten.blum@linux.dev>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/1] Compiler Attributes: disable __counted_by for clang < 19.1.3
2024-10-29 14:00 ` [PATCH 1/1] Compiler Attributes: " Jan Hendrik Farr
2024-10-29 15:10 ` Thorsten Blum
@ 2024-11-19 17:26 ` Kees Cook
2025-06-09 13:14 ` Dafna Hirschfeld
2 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2024-11-19 17:26 UTC (permalink / raw)
To: Jan Hendrik Farr
Cc: Kees Cook, nathan, ojeda, ndesaulniers, morbo, justinstitt,
thorsten.blum, ardb, oliver.sang, gustavoars, kent.overstreet,
arnd, gregkh, akpm, tavianator, linux-hardening, llvm,
linux-kernel, stable
On Tue, 29 Oct 2024 15:00:36 +0100, Jan Hendrik Farr wrote:
> 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
>
> [...]
Applied to for-next/hardening, thanks!
[1/1] Compiler Attributes: disable __counted_by for clang < 19.1.3
https://git.kernel.org/kees/c/f06e108a3dc5
Take care,
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/1] Compiler Attributes: disable __counted_by for clang < 19.1.3
2024-10-29 14:00 ` [PATCH 1/1] Compiler Attributes: " Jan Hendrik Farr
2024-10-29 15:10 ` Thorsten Blum
2024-11-19 17:26 ` Kees Cook
@ 2025-06-09 13:14 ` Dafna Hirschfeld
2025-06-09 13:51 ` Miguel Ojeda
2 siblings, 1 reply; 6+ messages in thread
From: Dafna Hirschfeld @ 2025-06-09 13:14 UTC (permalink / raw)
To: Jan Hendrik Farr
Cc: kees, nathan, ojeda, ndesaulniers, morbo, justinstitt,
thorsten.blum, ardb, oliver.sang, gustavoars, kent.overstreet,
arnd, gregkh, akpm, tavianator, linux-hardening, llvm,
linux-kernel, stable
On 29.10.2024 15:00, Jan Hendrik Farr wrote:
>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/#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>
>---
> 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(-)
>
>diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
>index 62ba01525479..376047beea3d 100644
>--- 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))
>diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
>index 32284cd26d52..c16d4199bf92 100644
>--- a/include/linux/compiler_attributes.h
>+++ b/include/linux/compiler_attributes.h
>@@ -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
>-
Why is the define of __counted_by moved from here (compiler_attributes.h)
to a different location (compiler_types.h) ?
I am asking this because I try to compile an out of tree kernel module with ofed headers.
in the ofed header of compiler_types.h there is an added include of types.h:
#include_next <linux/compiler_attributes.h>
#include <linux/types.h>
so what happen is that __counted_by is defined in types.h, and then I get a compilation error:
././include/linux/compiler_types.h:323: error: "__counted_by" redefined [-Werror]
I am not sure yet how this should be fixed.
Thank you,
Dafna
> /*
> * Optional: not supported by gcc
> * Optional: only supported since clang >= 14.0
>diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
>index 1a957ea2f4fe..639be0f30b45 100644
>--- a/include/linux/compiler_types.h
>+++ b/include/linux/compiler_types.h
>@@ -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.
> */
>diff --git a/init/Kconfig b/init/Kconfig
>index 530a382ee0fe..92f106cf5572 100644
>--- a/init/Kconfig
>+++ b/init/Kconfig
>@@ -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))
>diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c
>index 2abc78367dd1..5222c6393f11 100644
>--- a/lib/overflow_kunit.c
>+++ b/lib/overflow_kunit.c
>@@ -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);
>--
>2.47.0
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/1] Compiler Attributes: disable __counted_by for clang < 19.1.3
2025-06-09 13:14 ` Dafna Hirschfeld
@ 2025-06-09 13:51 ` Miguel Ojeda
0 siblings, 0 replies; 6+ messages in thread
From: Miguel Ojeda @ 2025-06-09 13:51 UTC (permalink / raw)
To: Dafna Hirschfeld
Cc: Jan Hendrik Farr, kees, nathan, ojeda, ndesaulniers, morbo,
justinstitt, thorsten.blum, ardb, oliver.sang, gustavoars,
kent.overstreet, arnd, gregkh, akpm, tavianator, linux-hardening,
llvm, linux-kernel, stable
On Mon, Jun 9, 2025 at 3:14 PM Dafna Hirschfeld
<dafna.hirschfeld@intel.com> wrote:
>
> Why is the define of __counted_by moved from here (compiler_attributes.h)
> to a different location (compiler_types.h) ?
`compiler_attributes.h` is supposed to have only things that do not
depend on the kernel configuration and so on.
It sounds like those out-of-tree headers should be fixed.
I hope that helps.
Cheers,
Miguel
^ permalink raw reply [flat|nested] 6+ messages in thread