| Date | Sun, 05 Feb 2012 23:09:53 +0100 | From | Willy Tarreau <> | Subject | [PATCH 04/91] agp: fix arbitrary kernel memory writes |
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2.6.27-longterm review patch. If anyone has any objections, please let us know.
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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 files changed, 8 insertions(+), 3 deletions(-)
Index: longterm-2.6.27/drivers/char/agp/generic.c =================================================================== --- longterm-2.6.27.orig/drivers/char/agp/generic.c 2012-02-05 22:34:34.961915038 +0100 +++ longterm-2.6.27/drivers/char/agp/generic.c 2012-02-05 22:34:35.500916106 +0100 @@ -1099,8 +1099,8 @@ 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; @@ -1132,7 +1132,7 @@ { size_t i; struct agp_bridge_data *bridge; - int mask_type; + int mask_type, num_entries; bridge = mem->bridge; if (!bridge) @@ -1144,6 +1144,11 @@ 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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