From: Rich Felker <dalias@aerifal.cx>
Date: Fri, 7 Dec 2012 02:12:28 +0000 (-0500)
Subject: fix invalid read in aligned_alloc
X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=commitdiff_plain;h=2ad9cf52eb9fea12a19bcf893828e1361a0b6546

fix invalid read in aligned_alloc

in case of mmap-obtained chunks, end points past the end of the
mapping and reading it may fault. since the value is not needed until
after the conditional, move the access to prevent invalid reads.
---

diff --git a/src/malloc/aligned_alloc.c b/src/malloc/aligned_alloc.c
index d623420b..158dba41 100644
--- a/src/malloc/aligned_alloc.c
+++ b/src/malloc/aligned_alloc.c
@@ -31,8 +31,6 @@ void *aligned_alloc(size_t align, size_t len)
 		return NULL;
 
 	header = ((size_t *)mem)[-1];
-	end = mem + (header & -8);
-	footer = ((size_t *)end)[-2];
 	new = (void *)((uintptr_t)mem + align-1 & -align);
 
 	if (!(header & 7)) {
@@ -41,6 +39,9 @@ void *aligned_alloc(size_t align, size_t len)
 		return new;
 	}
 
+	end = mem + (header & -8);
+	footer = ((size_t *)end)[-2];
+
 	((size_t *)mem)[-1] = header&7 | new-mem;
 	((size_t *)new)[-2] = footer&7 | new-mem;
 	((size_t *)new)[-1] = header&7 | end-new;