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Message-ID: <CAGG=3QWX0Koj3xNHiRHdiYupy4bFsJ6nNWWcCJkqbu8-GnmfZA@mail.gmail.com> Date: Mon, 6 Nov 2023 00:47:16 -0800 From: Bill Wendling <morbo@...gle.com> To: Kees Cook <keescook@...omium.org> Cc: KP Singh <kpsingh@...nel.org>, linux-hardening@...r.kernel.org, kernel test robot <lkp@...el.com>, "Gustavo A. R. Silva" <gustavoars@...nel.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] gcc-plugins: randstruct: Only warn about true flexible arrays On Sat, Nov 4, 2023 at 1:43 PM Kees Cook <keescook@...omium.org> wrote: > > The randstruct GCC plugin tried to discover "fake" flexible arrays > to issue warnings about them in randomized structs. In the future > LSM overhead reduction series, it would be legal to have a randomized > struct with a 1-element array, and this should _not_ be treated as a > flexible array, especially since commit df8fc4e934c1 ("kbuild: Enable > -fstrict-flex-arrays=3"). Disable the 0-sized and 1-element array > discovery logic in the plugin, but keep the "true" flexible array check. > > Cc: KP Singh <kpsingh@...nel.org> > Cc: linux-hardening@...r.kernel.org > Reported-by: kernel test robot <lkp@...el.com> > Closes: https://lore.kernel.org/oe-kbuild-all/202311021532.iBwuZUZ0-lkp@intel.com/ > Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") > Signed-off-by: Kees Cook <keescook@...omium.org> Reviewed-by: Bill Wendling <morbo@...gle.com> > --- > scripts/gcc-plugins/randomize_layout_plugin.c | 10 ---------- > 1 file changed, 10 deletions(-) > > diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c > index 366395cab490..910bd21d08f4 100644 > --- a/scripts/gcc-plugins/randomize_layout_plugin.c > +++ b/scripts/gcc-plugins/randomize_layout_plugin.c > @@ -278,8 +278,6 @@ static bool is_flexible_array(const_tree field) > { > const_tree fieldtype; > const_tree typesize; > - const_tree elemtype; > - const_tree elemsize; > > fieldtype = TREE_TYPE(field); > typesize = TYPE_SIZE(fieldtype); > @@ -287,20 +285,12 @@ static bool is_flexible_array(const_tree field) > if (TREE_CODE(fieldtype) != ARRAY_TYPE) > return false; > > - elemtype = TREE_TYPE(fieldtype); > - elemsize = TYPE_SIZE(elemtype); > - > /* size of type is represented in bits */ > > if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE && > TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE) > return true; > > - if (typesize != NULL_TREE && > - (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) || > - tree_to_uhwi(typesize) == tree_to_uhwi(elemsize)))) > - return true; > - > return false; > } > > -- > 2.34.1 > >
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