4.19-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook keescook@chromium.org
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@vger.kernel.org Cc: stable@vger.kernel.org Reported-by: Lukas Loidolt e1634039@student.tuwien.ac.at Closes: https://lore.kernel.org/all/f3ca77f0-e414-4065-83a5-ae4c4d25545d@student.tuw... Fixes: 313dd1b62921 ("gcc-plugins: Add the randstruct plugin") Signed-off-by: Kees Cook keescook@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 @@ -209,12 +209,14 @@ 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); @@ -224,11 +226,14 @@ 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;