From 8fad00b0b647ee662ce4737ca15be033b7a21714 Mon Sep 17 00:00:00 2001 From: Tobias Stoeckmann Date: Sun, 25 Sep 2016 21:42:09 +0200 Subject: Avoid OOB write in XRenderQueryFilters The memory for filter names is reserved right after receiving the reply. After that, filters are iterated and each individual filter name is stored in that reserved memory. The individual name lengths are not checked for validity, which means that a malicious server can reserve less memory than it will write to during each iteration. v2: consume remaining bytes in reply buffer on error. Signed-off-by: Tobias Stoeckmann Reviewed-by: Matthieu Herrb --- src/Filter.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/src/Filter.c b/src/Filter.c index edfa572..8d701eb 100644 --- a/src/Filter.c +++ b/src/Filter.c @@ -38,7 +38,7 @@ XRenderQueryFilters (Display *dpy, Drawable drawable) char *name; char len; int i; - unsigned long nbytes, nbytesAlias, nbytesName; + unsigned long nbytes, nbytesAlias, nbytesName, reply_left; if (!RenderHasExtension (info)) return NULL; @@ -114,6 +114,7 @@ XRenderQueryFilters (Display *dpy, Drawable drawable) * Read the filter aliases */ _XRead16Pad (dpy, filters->alias, 2 * rep.numAliases); + reply_left = 8 + rep.length - 2 * rep.numAliases;; /* * Read the filter names @@ -122,9 +123,19 @@ XRenderQueryFilters (Display *dpy, Drawable drawable) { int l; _XRead (dpy, &len, 1); + reply_left--; l = len & 0xff; + if ((unsigned long)l + 1 > nbytesName) { + _XEatDataWords(dpy, reply_left); + Xfree(filters); + UnlockDisplay (dpy); + SyncHandle (); + return NULL; + } + nbytesName -= l + 1; filters->filter[i] = name; _XRead (dpy, name, l); + reply_left -= l; name[l] = '\0'; name += l + 1; } -- cgit v1.2.1