From: Rich Felker <dalias@aerifal.cx>
Date: Sun, 4 Sep 2011 04:06:01 +0000 (-0400)
Subject: fix twos complement overflow bug in mem streams boundary check
X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=commitdiff_plain;h=32d67e938e8da0f37c59247acee8b10eaf9a113c

fix twos complement overflow bug in mem streams boundary check

the expression -off is not safe in case off is the most-negative
value. instead apply - to base which is known to be non-negative and
bounded within sanity.
---

diff --git a/src/stdio/open_memstream.c b/src/stdio/open_memstream.c
index 2f3569f1..57737098 100644
--- a/src/stdio/open_memstream.c
+++ b/src/stdio/open_memstream.c
@@ -28,7 +28,7 @@ static off_t ms_seek(FILE *f, off_t off, int whence)
 		errno = EINVAL;
 		return -1;
 	}
-	if (-off > base || off > SSIZE_MAX-base) goto fail;
+	if (off < -base || off > SSIZE_MAX-base) goto fail;
 	return c->pos = base+off;
 }
 
diff --git a/src/stdio/open_wmemstream.c b/src/stdio/open_wmemstream.c
index 3bc0f254..41b92d21 100644
--- a/src/stdio/open_wmemstream.c
+++ b/src/stdio/open_wmemstream.c
@@ -29,7 +29,7 @@ static off_t wms_seek(FILE *f, off_t off, int whence)
 		errno = EINVAL;
 		return -1;
 	}
-	if (-off > base || off > SSIZE_MAX/4-base) goto fail;
+	if (off < -base || off > SSIZE_MAX/4-base) goto fail;
 	memset(&c->mbs, 0, sizeof c->mbs);
 	return c->pos = base+off;
 }