apparmor/apparmor-2.5.1-fix-parser-use-after-free

From: Jeff Mahoney <jeffm@suse.com>
Subject: apparmor: Fix use after free in regexp parser

 There are two cases of use-after-free in the simply_tree_base code. It
 worked in the past because there aren't any allocations between the
 free and the use, so it was still around.

 With glibc's memory perturbing feature (set _MALLOC_PERTURB to anything),
 the freed memory is poisoned. This causes crashes in e.g. apparmor_parser
 while parsing certain profiles.

 This patch addresses it by saving a pointer to the node to free after
 the node is advanced.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
---
 parser/libapparmor_re/regexp.yy |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/parser/libapparmor_re/regexp.yy
+++ b/parser/libapparmor_re/regexp.yy
@@ -720,17 +720,19 @@ Node *simplify_tree_base(Node *t, int di
 		Node *i = t->child[!dir];
 		for (;dynamic_cast<AltNode *>(i); p = i, i = i->child[!dir]) {
 			if (t->child[dir]->eq(i->child[dir])) {
+				Node *old = t;
 				t->child[!dir]->dup();
-				t->release();
 				t = t->child[!dir];
+				old->release();
 				continue;
 			}
 		}
 		// last altnode of chain check other dir as well
 		if (t->child[dir]->eq(p->child[!dir])) {
+			Node *old = t;
 			t->child[!dir]->dup();
-			t->release();
 			t = t->child[!dir];
+			old->release();
 			continue;
 		}