| Message ID | 20250303214929.work.499-kees@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Commit | 3e58204299808848e80904f7166e0f0d7ffa588f |
| Headers | show |
| Series | hardening: Enable i386 FORTIFY_SOURCE on Clang 16+ | expand |
On Mon, Mar 03, 2025 at 01:49:37PM -0800, Kees Cook wrote: > The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed > in Clang 16[1]. > > Link: https://github.com/llvm/llvm-project/commit/c167c0a4dcdb998affb2756ce76903a12f7d8ca5 [1] > Signed-off-by: Kees Cook <kees@kernel.org> Yes, thank you for catching this! Reviewed-by: Nathan Chancellor <nathan@kernel.org> I assume you'll take this? > --- > Cc: Nathan Chancellor <nathan@kernel.org> > Cc: Nick Desaulniers <ndesaulniers@google.com> > Cc: Bill Wendling <morbo@google.com> > Cc: Justin Stitt <justinstitt@google.com> > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Cc: llvm@lists.linux.dev > Cc: linux-hardening@vger.kernel.org > --- > security/Kconfig.hardening | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening > index 23ffb0d7c845..c17366ce8224 100644 > --- a/security/Kconfig.hardening > +++ b/security/Kconfig.hardening > @@ -286,7 +286,7 @@ config FORTIFY_SOURCE > bool "Harden common str/mem functions against buffer overflows" > depends on ARCH_HAS_FORTIFY_SOURCE > # https://github.com/llvm/llvm-project/issues/53645 > - depends on !CC_IS_CLANG || !X86_32 > + depends on !X86_32 || !CC_IS_CLANG || CLANG_VERSION >= 160000 > help > Detect overflows of buffers in common string and memory functions > where the compiler can determine and validate the buffer sizes. > -- > 2.34.1 >
On Mon, 03 Mar 2025 13:49:37 -0800, Kees Cook wrote: > The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed > in Clang 16[1]. > > Applied to for-next/hardening, thanks! [1/1] hardening: Enable i386 FORTIFY_SOURCE on Clang 16+ https://git.kernel.org/kees/c/3e5820429980 Take care,
On Tue, Mar 04, 2025 at 09:50:44AM -0800, Kees Cook wrote: > On Mon, 03 Mar 2025 13:49:37 -0800, Kees Cook wrote: > > The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed > > in Clang 16[1]. > > > > > > Applied to for-next/hardening, thanks! > > [1/1] hardening: Enable i386 FORTIFY_SOURCE on Clang 16+ > https://git.kernel.org/kees/c/3e5820429980 Turns out this is actually incomplete based on my testing, I see the following warnings with ARCH=i386 allmodconfig with all supported clang versions: warning: unsafe strcpy() usage lacked '__write_overflow' symbol in lib/test_fortify/write_overflow-strcpy-lit.c warning: unsafe strcpy() usage lacked '__write_overflow' symbol in lib/test_fortify/write_overflow-strcpy.c We also need to drop '-ffreestanding' from arch/x86/Makefile (which Nick has mentioned in [1]). Time to revive [2]? :) or just do it in this patch, since it sounds like there was no regression with GCC? [1]: https://github.com/ClangBuiltLinux/linux/issues/1583#issuecomment-1123016466 [2]: https://lore.kernel.org/20200817220212.338670-5-ndesaulniers@google.com/ Cheers, Nathan
On March 7, 2025 1:47:34 PM PST, Nathan Chancellor <nathan@kernel.org> wrote: >On Tue, Mar 04, 2025 at 09:50:44AM -0800, Kees Cook wrote: >> On Mon, 03 Mar 2025 13:49:37 -0800, Kees Cook wrote: >> > The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed >> > in Clang 16[1]. >> > >> > >> >> Applied to for-next/hardening, thanks! >> >> [1/1] hardening: Enable i386 FORTIFY_SOURCE on Clang 16+ >> https://git.kernel.org/kees/c/3e5820429980 > >Turns out this is actually incomplete based on my testing, I see the >following warnings with ARCH=i386 allmodconfig with all supported clang >versions: > > warning: unsafe strcpy() usage lacked '__write_overflow' symbol in lib/test_fortify/write_overflow-strcpy-lit.c > warning: unsafe strcpy() usage lacked '__write_overflow' symbol in lib/test_fortify/write_overflow-strcpy.c > >We also need to drop '-ffreestanding' from arch/x86/Makefile (which Nick >has mentioned in [1]). Time to revive [2]? :) or just do it in this >patch, since it sounds like there was no regression with GCC? > >[1]: https://github.com/ClangBuiltLinux/linux/issues/1583#issuecomment-1123016466 >[2]: https://lore.kernel.org/20200817220212.338670-5-ndesaulniers@google.com/ Oh good catch! Probably I need to do this in two patches just to be safe: - make -ffreestanding be Clang only - switch to version checks for FORTIFY and freestanding That will split the changes for GCC and Clang into separate patches. Or maybe that's overkill? -Kees
On Fri, Mar 07, 2025 at 02:57:06PM -0800, Kees Cook wrote: > > > On March 7, 2025 1:47:34 PM PST, Nathan Chancellor <nathan@kernel.org> wrote: > >On Tue, Mar 04, 2025 at 09:50:44AM -0800, Kees Cook wrote: > >> On Mon, 03 Mar 2025 13:49:37 -0800, Kees Cook wrote: > >> > The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed > >> > in Clang 16[1]. > >> > > >> > > >> > >> Applied to for-next/hardening, thanks! > >> > >> [1/1] hardening: Enable i386 FORTIFY_SOURCE on Clang 16+ > >> https://git.kernel.org/kees/c/3e5820429980 > > > >Turns out this is actually incomplete based on my testing, I see the > >following warnings with ARCH=i386 allmodconfig with all supported clang > >versions: > > > > warning: unsafe strcpy() usage lacked '__write_overflow' symbol in lib/test_fortify/write_overflow-strcpy-lit.c > > warning: unsafe strcpy() usage lacked '__write_overflow' symbol in lib/test_fortify/write_overflow-strcpy.c > > > >We also need to drop '-ffreestanding' from arch/x86/Makefile (which Nick > >has mentioned in [1]). Time to revive [2]? :) or just do it in this > >patch, since it sounds like there was no regression with GCC? > > > >[1]: https://github.com/ClangBuiltLinux/linux/issues/1583#issuecomment-1123016466 > >[2]: https://lore.kernel.org/20200817220212.338670-5-ndesaulniers@google.com/ > > Oh good catch! Probably I need to do this in two patches just to be safe: > - make -ffreestanding be Clang only > - switch to version checks for FORTIFY and freestanding > > That will split the changes for GCC and Clang into separate patches. Or maybe that's overkill? No, I think that is reasonable, as any regressions with GCC would be noticed by the first change, rather than being mixed in with the second. It should also make it easier to drop that when the minimum version of clang gets bumped to 16 (either for the whole kernel or just x86, like the bump to 15 this dev cycle for the recent stack protector fixes in -top). Cheers, Nathan
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 23ffb0d7c845..c17366ce8224 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -286,7 +286,7 @@ config FORTIFY_SOURCE bool "Harden common str/mem functions against buffer overflows" depends on ARCH_HAS_FORTIFY_SOURCE # https://github.com/llvm/llvm-project/issues/53645 - depends on !CC_IS_CLANG || !X86_32 + depends on !X86_32 || !CC_IS_CLANG || CLANG_VERSION >= 160000 help Detect overflows of buffers in common string and memory functions where the compiler can determine and validate the buffer sizes.
The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed in Clang 16[1]. Link: https://github.com/llvm/llvm-project/commit/c167c0a4dcdb998affb2756ce76903a12f7d8ca5 [1] Signed-off-by: Kees Cook <kees@kernel.org> --- Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Bill Wendling <morbo@google.com> Cc: Justin Stitt <justinstitt@google.com> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> Cc: llvm@lists.linux.dev Cc: linux-hardening@vger.kernel.org --- security/Kconfig.hardening | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)