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agp: fix arbitrary kernel memory writes 

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>
This commit is contained in:
Vasiliy Kulikov 2011-04-14 20:55:16 +04:00 committed by Dave Airlie
parent b522f02184
commit 194b3da873
1 changed files with 8 additions and 3 deletions
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11
drivers/char/agp/generic.c
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@ -1095,8 +1095,8 @@ 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;
@ -1130,7 +1130,7 @@ 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)
@ -1142,6 +1142,11 @@ 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 */