Patch "gcc-plugins: randstruct: Only warn about true flexible arrays" has been added to the 6.5-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    gcc-plugins: randstruct: Only warn about true flexible arrays

to the 6.5-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     gcc-plugins-randstruct-only-warn-about-true-flexible.patch
and it can be found in the queue-6.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f339446de391ebb8f3298aa3501c486f915624bc
Author: Kees Cook <keescook@xxxxxxxxxxxx>
Date:   Sat Nov 4 13:43:37 2023 -0700

    gcc-plugins: randstruct: Only warn about true flexible arrays
    
    [ Upstream commit 1ee60356c2dca938362528404af95b8ef3e49b6a ]
    
    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@xxxxxxxxxx>
    Cc: linux-hardening@xxxxxxxxxxxxxxx
    Reported-by: kernel test robot <lkp@xxxxxxxxx>
    Closes: https://lore.kernel.org/oe-kbuild-all/202311021532.iBwuZUZ0-lkp@xxxxxxxxx/
    Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3")
    Reviewed-by: Bill Wendling <morbo@xxxxxxxxxx>
    Acked-by: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20231104204334.work.160-kees@xxxxxxxxxx
    Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
index 951b74ba1b242..5e5744b65f8a9 100644
--- a/scripts/gcc-plugins/randomize_layout_plugin.c
+++ b/scripts/gcc-plugins/randomize_layout_plugin.c
@@ -273,8 +273,6 @@ 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);
@@ -282,20 +280,12 @@ 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;
 }