Clang has never correctly compiled the FORTIFY_SOURCE defenses due to a couple bugs:
Eliding inlines with matching __builtin_* names https://bugs.llvm.org/show_bug.cgi?id=50322
Incorrect __builtin_constant_p() of some globals https://bugs.llvm.org/show_bug.cgi?id=41459
In the process of making improvements to the FORTIFY_SOURCE defenses, the first (silent) bug (coincidentally) becomes worked around, but exposes the latter which breaks the build. As such, Clang must not be used with CONFIG_FORTIFY_SOURCE until at least latter bug is fixed (in Clang 13), and the fortify routines have been rearranged.
Update the Kconfig to reflect the reality of the current situation.
Signed-off-by: Kees Cook keescook@chromium.org --- security/Kconfig | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/security/Kconfig b/security/Kconfig index 0ced7fd33e4d..8f0e675e70a4 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -191,6 +191,9 @@ config HARDENED_USERCOPY_PAGESPAN config FORTIFY_SOURCE bool "Harden common str/mem functions against buffer overflows" depends on ARCH_HAS_FORTIFY_SOURCE + # https://bugs.llvm.org/show_bug.cgi?id=50322 + # https://bugs.llvm.org/show_bug.cgi?id=41459 + depends on !CONFIG_CC_IS_CLANG help Detect overflows of buffers in common string and memory functions where the compiler can determine and validate the buffer sizes.