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Date: Mon, 31 Jan 2022 13:09:41 -0800 From: Kees Cook <keescook@...omium.org> To: Nick Desaulniers <ndesaulniers@...gle.com> Cc: Nathan Chancellor <nathan@...nel.org>, linux-hardening@...r.kernel.org, llvm@...ts.linux.dev, linux-kernel@...r.kernel.org Subject: Re: [PATCH] fortify: Update compile-time tests for Clang 14 On Mon, Jan 31, 2022 at 11:09:27AM -0800, Nick Desaulniers wrote: > On Sun, Jan 30, 2022 at 10:16 AM Kees Cook <keescook@...omium.org> wrote: > > > > Clang 14 introduces support for compiletime_assert(). Update the > > compile-time warning regex to catch Clang's variant of the warning text > > in preparation for Clang supporting CONFIG_FORTIFY_SOURCE. > > https://twitter.com/ifosteve/status/1190348262500421634?lang=en > error messages can change over time. More thoughts below. Sure, but I don't want the compile-time checks to silently regress, which requires looking specifically for the error. > > Cc: Nathan Chancellor <nathan@...nel.org> > > Cc: Nick Desaulniers <ndesaulniers@...gle.com> > > Cc: linux-hardening@...r.kernel.org > > Cc: llvm@...ts.linux.dev > > Signed-off-by: Kees Cook <keescook@...omium.org> > > --- > > I'm splitting this patch out of the main Clang FORTIFY enabling patch. > > --- > > scripts/test_fortify.sh | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/scripts/test_fortify.sh b/scripts/test_fortify.sh > > index a4da365508f0..c2688ab8281d 100644 > > --- a/scripts/test_fortify.sh > > +++ b/scripts/test_fortify.sh > > @@ -46,8 +46,12 @@ if "$@" -Werror -c "$IN" -o "$OUT".o 2> "$TMP" ; then > > status="warning: unsafe ${FUNC}() usage lacked '$WANT' symbol in $IN" > > fi > > else > > - # If the build failed, check for the warning in the stderr (gcc). > > - if ! grep -q -m1 "error: call to .\b${WANT}\b." "$TMP" ; then > > + # If the build failed, check for the warning in the stderr. > > + # GCC: > > + # ./include/linux/fortify-string.h:316:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] > > + # Clang 14: > > + # ./include/linux/fortify-string.h:316:4: error: call to __write_overflow_field declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror,-Wattribute-warning] > > + if ! grep -Eq -m1 "error: call to .?\b${WANT}\b.?" "$TMP" ; then > > Doesn't this depend on -Werror being set? I guess it did so before > hand, too, but couldn't I unset CONFIG_WERROR then this check would > still fail (since instead of `error:` we'd have `warning:`)? If we > used __attribute__((error(""))) then this would always be an error. > Right now, it is only because -Werror is set promoting the warning > diagnostic to an error. Right, see earlier up in the script. "-Werror" is explicitly set: line 40: if "$@" -Werror -c "$IN" -o "$OUT".o 2> "$TMP" ; then -- Kees Cook
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