linux-kernel - [PATCH] [5/98] agp: fix arbitrary kernel memory writes

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Date:	Tue, 26 Jul 2011 17:34:57 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	segoon@...nwall.com, airlied@...hat.com, ak@...ux.intel.com,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	tim.bird@...sony.com, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH] [5/98] agp: fix arbitrary kernel memory writes

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Vasiliy Kulikov <segoon@...nwall.com>

[ upstream commit 194b3da873fd334ef183806db751473512af29ce ]

pg_start is copied from userspace on AGPIOC_BIND and AGPIOC_UNBIND ioctl
cmds of agp_ioctl() and passed to agpioc_bind_wrap().  As said in the
comment, (pg_start + mem->page_count) may wrap in case of AGPIOC_BIND,
and it is not checked at all in case of AGPIOC_UNBIND.  As a result, user
with sufficient privileges (usually "video" group) may generate either
local DoS or privilege escalation.

Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

Index: linux-2.6.35.y/drivers/char/agp/generic.c
===================================================================
--- linux-2.6.35.y.orig/drivers/char/agp/generic.c
+++ linux-2.6.35.y/drivers/char/agp/generic.c
@@ -1122,8 +1122,8 @@ int agp_generic_insert_memory(struct agp
 		return -EINVAL;
 	}
 
-	/* AK: could wrap */
-	if ((pg_start + mem->page_count) > num_entries)
+	if (((pg_start + mem->page_count) > num_entries) ||
+	    ((pg_start + mem->page_count) < pg_start))
 		return -EINVAL;
 
 	j = pg_start;
@@ -1157,7 +1157,7 @@ int agp_generic_remove_memory(struct agp
 {
 	size_t i;
 	struct agp_bridge_data *bridge;
-	int mask_type;
+	int mask_type, num_entries;
 
 	bridge = mem->bridge;
 	if (!bridge)
@@ -1169,6 +1169,11 @@ int agp_generic_remove_memory(struct agp
 	if (type != mem->type)
 		return -EINVAL;
 
+	num_entries = agp_num_entries();
+	if (((pg_start + mem->page_count) > num_entries) ||
+	    ((pg_start + mem->page_count) < pg_start))
+		return -EINVAL;
+
 	mask_type = bridge->driver->agp_type_to_mask_type(bridge, type);
 	if (mask_type != 0) {
 		/* The generic routines know nothing of memory types */
--
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