6.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook <keescook@xxxxxxxxxxxx> commit 381fdb73d1e2a48244de7260550e453d1003bb8e upstream. The performance mode of the gcc-plugin randstruct was shuffling struct members outside of the cache-line groups. Limit the range to the specified group indexes. Cc: linux-hardening@xxxxxxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Reported-by: Lukas Loidolt <e1634039@xxxxxxxxxxxxxxxxxxxx> Closes: https://lore.kernel.org/all/f3ca77f0-e414-4065-83a5-ae4c4d25545d@xxxxxxxxxxxxxxxxxxxx Fixes: 313dd1b62921 ("gcc-plugins: Add the randstruct plugin") Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- scripts/gcc-plugins/randomize_layout_plugin.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/scripts/gcc-plugins/randomize_layout_plugin.c +++ b/scripts/gcc-plugins/randomize_layout_plugin.c @@ -191,12 +191,14 @@ static void partition_struct(tree *field static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state) { - unsigned long i, x; + unsigned long i, x, index; struct partition_group size_group[length]; unsigned long num_groups = 0; unsigned long randnum; partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups); + + /* FIXME: this group shuffle is currently a no-op. */ for (i = num_groups - 1; i > 0; i--) { struct partition_group tmp; randnum = ranval(prng_state) % (i + 1); @@ -206,11 +208,14 @@ static void performance_shuffle(tree *ne } for (x = 0; x < num_groups; x++) { - for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) { + for (index = size_group[x].length - 1; index > 0; index--) { tree tmp; + + i = size_group[x].start + index; if (DECL_BIT_FIELD_TYPE(newtree[i])) continue; - randnum = ranval(prng_state) % (i + 1); + randnum = ranval(prng_state) % (index + 1); + randnum += size_group[x].start; // we could handle this case differently if desired if (DECL_BIT_FIELD_TYPE(newtree[randnum])) continue;
