From 36f1dae749acb065eaefca56d42d19ef6822a001 Mon Sep 17 00:00:00 2001 From: Mike DePaulo Date: Sun, 8 Feb 2015 20:53:14 -0500 Subject: [PATCH 06/40] CVE-2014-0209: integer overflow of realloc() size in lexAlias() from xorg/lib/libXfont commit 05c8020a49416dd8b7510cbba45ce4f3fc81a7dc lexAlias() reads from a file in a loop. It does this by starting with a 64 byte buffer. If that size limit is hit, it does a realloc of the buffer size << 1, basically doubling the needed length every time the length limit is hit. Eventually, this will shift out to 0 (for a length of ~4gig), and that length will be passed on to realloc(). A length of 0 (with a valid pointer) causes realloc to free the buffer on most POSIX platforms, but the caller will still have a pointer to it, leading to use after free issues. --- nx-X11/lib/font/fontfile/dirfile.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/nx-X11/lib/font/fontfile/dirfile.c b/nx-X11/lib/font/fontfile/dirfile.c index f390391..3a2fead 100644 --- a/nx-X11/lib/font/fontfile/dirfile.c +++ b/nx-X11/lib/font/fontfile/dirfile.c @@ -45,6 +45,7 @@ in this Software without prior written authorization from The Open Group. #include #include #include +#include static Bool AddFileNameAliases ( FontDirectoryPtr dir ); static int ReadFontAlias ( char *directory, Bool isFile, @@ -373,6 +374,9 @@ lexAlias(FILE *file, char **lexToken) int nsize; char *nbuf; + if (tokenSize >= (INT_MAX >> 2)) + /* Stop before we overflow */ + return EALLOC; nsize = tokenSize ? (tokenSize << 1) : 64; nbuf = (char *) xrealloc(tokenBuf, nsize); if (!nbuf) -- 2.1.4