1665N/AFrom 8fad00b0b647ee662ce4737ca15be033b7a21714 Mon Sep 17 00:00:00 2001

1665N/AFrom: Tobias Stoeckmann <tobias@stoeckmann.org>

1665N/ADate: Sun, 25 Sep 2016 21:42:09 +0200

1665N/ASubject: [PATCH:libXrender 1/2] Avoid OOB write in XRenderQueryFilters

1665N/A

1665N/AThe memory for filter names is reserved right after receiving the reply.

1665N/AAfter that, filters are iterated and each individual filter name is

1665N/Astored in that reserved memory.

1665N/A

1665N/AThe individual name lengths are not checked for validity, which means

1665N/Athat a malicious server can reserve less memory than it will write to

1665N/Aduring each iteration.

1665N/A

1665N/Av2: consume remaining bytes in reply buffer on error.

1665N/A

1665N/ASigned-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>

1665N/AReviewed-by: Matthieu Herrb <matthieu@herrb.eu>

1665N/A---

1665N/A src/Filter.c | 13 ++++++++++++-

1665N/A 1 file changed, 12 insertions(+), 1 deletion(-)

1665N/A

1665N/Adiff --git a/src/Filter.c b/src/Filter.c

1665N/Aindex edfa572..8d701eb 100644

1665N/A--- a/src/Filter.c

1665N/A+++ b/src/Filter.c

1665N/A@@ -38,7 +38,7 @@ XRenderQueryFilters (Display *dpy, Drawable drawable)

1665N/A char *name;

1665N/A char len;

1665N/A int i;

1665N/A- unsigned long nbytes, nbytesAlias, nbytesName;

1665N/A+ unsigned long nbytes, nbytesAlias, nbytesName, reply_left;

1665N/A

1665N/A if (!RenderHasExtension (info))

1665N/A return NULL;

1665N/A@@ -114,6 +114,7 @@ XRenderQueryFilters (Display *dpy, Drawable drawable)

1665N/A * Read the filter aliases

1665N/A */

1665N/A _XRead16Pad (dpy, filters->alias, 2 * rep.numAliases);

1665N/A+ reply_left = 8 + rep.length - 2 * rep.numAliases;;

1665N/A

1665N/A /*

1665N/A * Read the filter names

1665N/A@@ -122,9 +123,19 @@ XRenderQueryFilters (Display *dpy, Drawable drawable)

1665N/A {

1665N/A int l;

1665N/A _XRead (dpy, &len, 1);

1665N/A+ reply_left--;

1665N/A l = len & 0xff;

1665N/A+ if ((unsigned long)l + 1 > nbytesName) {

1665N/A+ _XEatDataWords(dpy, reply_left);

1665N/A+ Xfree(filters);

1665N/A+ UnlockDisplay (dpy);

1665N/A+ SyncHandle ();

1665N/A+ return NULL;

1665N/A+ }

1665N/A+ nbytesName -= l + 1;

1665N/A filters->filter[i] = name;

1665N/A _XRead (dpy, name, l);

1665N/A+ reply_left -= l;

1665N/A name[l] = '\0';

1665N/A name += l + 1;

1665N/A }

1665N/A--

1665N/A2.7.4

1665N/A