From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 27 Apr 2018 12:27:14 +0000 (+0200)
Subject: alloca: add an overflow check too
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=7ebe63f00f55a754c07c020c80fbbba799c30fda;p=elogind.git

alloca: add an overflow check too

Of course, alloca() shouldn't be used with anything that can grow
without bounds anyway, but let's better safe than sorry, and catch this
early.

Since alloca() is not supposed to return an error we trigger an
assert() instead, which is still better than heap trickery.
---

diff --git a/src/basic/alloc-util.h b/src/basic/alloc-util.h
index 88cd6b0bc..bae6a2845 100644
--- a/src/basic/alloc-util.h
+++ b/src/basic/alloc-util.h
@@ -18,9 +18,17 @@
 
 #define new0(t, n) ((t*) calloc((n), sizeof(t)))
 
-#define newa(t, n) ((t*) alloca(sizeof(t)*(n)))
+#define newa(t, n)                                              \
+        ({                                                      \
+                assert(!size_multiply_overflow(sizeof(t), n));  \
+                (t*) alloca(sizeof(t)*(n));                     \
+        })
 
-#define newa0(t, n) ((t*) alloca0(sizeof(t)*(n)))
+#define newa0(t, n)                                             \
+        ({                                                      \
+                assert(!size_multiply_overflow(sizeof(t), n));  \
+                (t*) alloca0(sizeof(t)*(n));                    \
+        })
 
 #define newdup(t, p, n) ((t*) memdup_multiply(p, sizeof(t), (n)))