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Subject[49/55] agp: fix arbitrary kernel memory writes
2.6.38-stable review patch.  If anyone has any objections, please let us know.

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

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@openwall.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/char/agp/generic.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
--- a/drivers/char/agp/generic.c
+++ b/drivers/char/agp/generic.c
@@ -1089,8 +1089,8 @@ 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;
@@ -1124,7 +1124,7 @@ 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)
@@ -1136,6 +1136,11 @@ 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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