From: Geert Uytterhoeven Date: Fri, 8 Dec 2017 13:13:02 +0000 (+0100) Subject: of: overlay: Fix out-of-bounds write in init_overlay_changeset() X-Git-Tag: v4.15-rc3~12^2~1 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=35e691eddca565f475ba69ff84ca0c9db3b3257b;p=linux.git of: overlay: Fix out-of-bounds write in init_overlay_changeset() If an overlay has no "__symbols__" node, but it has nodes without "__overlay__" subnodes at the end (e.g. a "__fixups__" node), after filling in all fragments for nodes with "__overlay__" subnodes, "fragment = &fragments[cnt]" will point beyond the end of the allocated array. Hence writing to "fragment->overlay" will overwrite unallocated memory, which may lead to a crash later. Fix this by deferring both the assignment to "fragment" and the offending write afterwards until we know for sure the node has an "__overlay__" subnode, and thus a valid entry in "fragments[]". Fixes: 61b4de4e0b384f4a ("of: overlay: minor restructuring") Signed-off-by: Geert Uytterhoeven Signed-off-by: Rob Herring --- diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c index fcce5cdbe229..83bb2edfc65c 100644 --- a/drivers/of/overlay.c +++ b/drivers/of/overlay.c @@ -572,9 +572,10 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs, cnt = 0; for_each_child_of_node(tree, node) { - fragment = &fragments[cnt]; - fragment->overlay = of_get_child_by_name(node, "__overlay__"); - if (fragment->overlay) { + overlay_node = of_get_child_by_name(node, "__overlay__"); + if (overlay_node) { + fragment = &fragments[cnt]; + fragment->overlay = overlay_node; fragment->target = find_target_node(node); if (!fragment->target) { of_node_put(fragment->overlay);