From 7909f70e73f40113608fba3ddb657c05c3276da1 Mon Sep 17 00:00:00 2001 From: Alan Coopersmith Date: Mon, 6 Jan 2014 23:30:14 -0800 Subject: [PATCH 03/31] dix: integer overflow in GetHosts() [CVE-2014-8092 2/4] GetHosts() iterates over all the hosts it has in memory, and copies them to a buffer. The buffer length is calculated by iterating over all the hosts and adding up all of their combined length. There is a potential integer overflow, if there are lots and lots of hosts (with a combined length of > ~4 gig). This should be possible by repeatedly calling ProcChangeHosts() on 64bit machines with enough memory. This patch caps the list at 1mb, because multi-megabyte hostname lists for X access control are insane. Reported-by: Ilja Van Sprundel Signed-off-by: Alan Coopersmith Reviewed-by: Peter Hutterer Signed-off-by: Fedora X Ninjas --- os/access.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/os/access.c b/os/access.c index 88a44d9..e7d668a 100644 --- a/os/access.c +++ b/os/access.c @@ -1323,6 +1323,10 @@ GetHosts(pointer *data, int *pnHosts, int *pLen, BOOL * pEnabled) for (host = validhosts; host; host = host->next) { nHosts++; n += pad_to_int32(host->len) + sizeof(xHostEntry); + /* Could check for INT_MAX, but in reality having more than 1mb of + hostnames in the access list is ridiculous */ + if (n >= 1048576) + break; } if (n) { *data = ptr = malloc(n); @@ -1331,6 +1335,8 @@ GetHosts(pointer *data, int *pnHosts, int *pLen, BOOL * pEnabled) } for (host = validhosts; host; host = host->next) { len = host->len; + if ((ptr + sizeof(xHostEntry) + len) > (data + n)) + break; ((xHostEntry *) ptr)->family = host->family; ((xHostEntry *) ptr)->length = len; ptr += sizeof(xHostEntry); -- 1.9.3