File xkbcomp-Don-t-falsely-promise-from-ExprResolveLhs.patch of Package libxkbcommon.31860

From 38e1766bc6e20108948aec8a0b222a4bad0254e9 Mon Sep 17 00:00:00 2001
From: Daniel Stone <daniels@collabora.com>
Date: Mon, 26 Jun 2017 17:21:45 +0100
Subject: [PATCH] xkbcomp: Don't falsely promise from ExprResolveLhs
Git-commit: 38e1766bc6e20108948aec8a0b222a4bad0254e9
Patch-mainline: xkbcommon-0.8.2
References: CVE-2018-15861

Every user of ExprReturnLhs goes on to unconditionally dereference the
field return, which can be NULL if xkb_intern_atom fails. Return false
if this is the case, so we fail safely.

Testcase: splice geometry data into interp

Signed-off-by: Daniel Stone <daniels@collabora.com>

---
 src/xkbcomp/expr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/xkbcomp/expr.c b/src/xkbcomp/expr.c
index 91713da..b5ab717 100644
--- a/src/xkbcomp/expr.c
+++ b/src/xkbcomp/expr.c
@@ -42,7 +42,7 @@ ExprResolveLhs(struct xkb_context *ctx, const ExprDef *expr,
         *elem_rtrn = NULL;
         *field_rtrn = xkb_atom_text(ctx, expr->ident.ident);
         *index_rtrn = NULL;
-        return true;
+        return (*field_rtrn != NULL);
     case EXPR_FIELD_REF:
         *elem_rtrn = xkb_atom_text(ctx, expr->field_ref.element);
         *field_rtrn = xkb_atom_text(ctx, expr->field_ref.field);
-- 
2.35.3