linux-kernel - [34-longterm 225/247] agp: fix arbitrary kernel memory writes

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Message-Id: <1308850515-15242-166-git-send-email-paul.gortmaker@windriver.com>
Date:	Thu, 23 Jun 2011 13:34:53 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Vasiliy Kulikov <segoon@...nwall.com>,
	Dave Airlie <airlied@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 225/247] agp: fix arbitrary kernel memory writes

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

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit 194b3da873fd334ef183806db751473512af29ce upstream.

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: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 drivers/char/agp/generic.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/char/agp/generic.c b/drivers/char/agp/generic.c
index fb86708..13a3446 100644
--- a/drivers/char/agp/generic.c
+++ b/drivers/char/agp/generic.c
@@ -1124,8 +1124,8 @@ int agp_generic_insert_memory(struct agp_memory * mem, off_t pg_start, int type)
 		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;
@@ -1159,7 +1159,7 @@ int agp_generic_remove_memory(struct agp_memory *mem, off_t pg_start, int type)
 {
 	size_t i;
 	struct agp_bridge_data *bridge;
-	int mask_type;
+	int mask_type, num_entries;
 
 	bridge = mem->bridge;
 	if (!bridge)
@@ -1171,6 +1171,11 @@ int agp_generic_remove_memory(struct agp_memory *mem, off_t pg_start, int type)
 	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 */
-- 
1.7.4.4

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