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- u_Avoid-use-after-free-in-dix-dixfonts.c-doImageText.patch

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* Fixes a security issue, in which an authenticated X client
   can cause an X server to use memory after it was freed, 
   potentially leading to crash and/or memory corruption.
   (CVE-2013-4396, bnc#843652)

OBS-URL: https://build.opensuse.org/package/show/X11:XOrg/xorg-x11-server?expand=0&rev=461
This commit is contained in:
Stefan Dirsch 2013-10-15 13:48:46 +00:00 committed by Git OBS Bridge
parent 0f0c8af996
commit bbc5acff6c
3 changed files with 86 additions and 0 deletions
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75
u_Avoid-use-after-free-in-dix-dixfonts.c-doImageText.patch Normal file
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@ -0,0 +1,75 @@
From a4d9bf1259ad28f54b6d59a480b2009cc89ca623 Mon Sep 17 00:00:00 2001
From: Alan Coopersmith <alan.coopersmith@oracle.com>
Date: Mon, 16 Sep 2013 21:47:16 -0700
Subject: [PATCH] Avoid use-after-free in dix/dixfonts.c: doImageText()
Save a pointer to the passed in closure structure before copying it
and overwriting the *c pointer to point to our copy instead of the
original. If we hit an error, once we free(c), reset c to point to
the original structure before jumping to the cleanup code that
references *c.
Since one of the errors being checked for is whether the server was
able to malloc(c->nChars * itemSize), the client can potentially pass
a number of characters chosen to cause the malloc to fail and the
error path to be taken, resulting in the read from freed memory.
Since the memory is accessed almost immediately afterwards, and the
X server is mostly single threaded, the odds of the free memory having
invalid contents are low with most malloc implementations when not using
memory debugging features, but some allocators will definitely overwrite
the memory there, leading to a likely crash.
Reported-by: Pedro Ribeiro <pedrib@gmail.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Julien Cristau <jcristau@debian.org>
---
dix/dixfonts.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/dix/dixfonts.c b/dix/dixfonts.c
index feb765d..2e34d37 100644
--- a/dix/dixfonts.c
+++ b/dix/dixfonts.c
@@ -1425,6 +1425,7 @@ doImageText(ClientPtr client, ITclosurePtr c)
GC *pGC;
unsigned char *data;
ITclosurePtr new_closure;
+ ITclosurePtr old_closure;
/* We're putting the client to sleep. We need to
save some state. Similar problem to that handled
@@ -1436,12 +1437,14 @@ doImageText(ClientPtr client, ITclosurePtr c)
err = BadAlloc;
goto bail;
}
+ old_closure = c;
*new_closure = *c;
c = new_closure;
data = malloc(c->nChars * itemSize);
if (!data) {
free(c);
+ c = old_closure;
err = BadAlloc;
goto bail;
}
@@ -1452,6 +1455,7 @@ doImageText(ClientPtr client, ITclosurePtr c)
if (!pGC) {
free(c->data);
free(c);
+ c = old_closure;
err = BadAlloc;
goto bail;
}
@@ -1464,6 +1468,7 @@ doImageText(ClientPtr client, ITclosurePtr c)
FreeScratchGC(pGC);
free(c->data);
free(c);
+ c = old_closure;
err = BadAlloc;
goto bail;
}
--
1.7.9.2

9
xorg-x11-server.changes
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@ -1,3 +1,12 @@
-------------------------------------------------------------------
Tue Oct 15 13:07:50 UTC 2013 - sndirsch@suse.com
- u_Avoid-use-after-free-in-dix-dixfonts.c-doImageText.patch
* Fixes a security issue, in which an authenticated X client
can cause an X server to use memory after it was freed,
potentially leading to crash and/or memory corruption.
(CVE-2013-4396, bnc#843652)
-------------------------------------------------------------------
Fri Sep 13 23:39:28 UTC 2013 - tobias.johannes.klausmann@mni.thm.de

2
xorg-x11-server.spec
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@ -156,6 +156,7 @@ Patch229: u_disable-acpi-code.patch
Patch230: u_xserver_xvfb-randr.patch
Patch240: U_revert_dri2_realloc_dri2_drawable_if-pixmap_serial_changes.patch
Patch241: u_Avoid-use-after-free-in-dix-dixfonts.c-doImageText.patch
%description
This package contains the X.Org Server.
@ -241,6 +242,7 @@ cp %{SOURCE96} .
%patch230 -p1
%patch240 -p1
%patch241 -p1
%build
autoreconf -fi