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    SubjectRe: [PATCH 31/64] fortify: Explicitly disable Clang support
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    Date
    On 7/27/2021 1:58 PM, Kees Cook wrote:
    > 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

    Should be !CC_IS_CLANG, Kconfig is hard :)

    > help
    > Detect overflows of buffers in common string and memory functions
    > where the compiler can determine and validate the buffer sizes.
    >

    Cheers,
    Nathan

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