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authorDaniel Borkmann <daniel@iogearbox.net>2015-11-30 13:02:56 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-12-14 21:24:32 -0800
commit879e7d33bea095c7c3ed51fc19a58b6001e26797 (patch)
tree9ab856d99c0eb53f6871daad25b1866264e776a3
parent28492d307272fa3090f026d559e0d3ea8328b4dd (diff)
bpf, array: fix heap out-of-bounds access when updating elements
[ Upstream commit fbca9d2d35c6ef1b323fae75cc9545005ba25097 ] During own review but also reported by Dmitry's syzkaller [1] it has been noticed that we trigger a heap out-of-bounds access on eBPF array maps when updating elements. This happens with each map whose map->value_size (specified during map creation time) is not multiple of 8 bytes. In array_map_alloc(), elem_size is round_up(attr->value_size, 8) and used to align array map slots for faster access. However, in function array_map_update_elem(), we update the element as ... memcpy(array->value + array->elem_size * index, value, array->elem_size); ... where we access 'value' out-of-bounds, since it was allocated from map_update_elem() from syscall side as kmalloc(map->value_size, GFP_USER) and later on copied through copy_from_user(value, uvalue, map->value_size). Thus, up to 7 bytes, we can access out-of-bounds. Same could happen from within an eBPF program, where in worst case we access beyond an eBPF program's designated stack. Since 1be7f75d1668 ("bpf: enable non-root eBPF programs") didn't hit an official release yet, it only affects priviledged users. In case of array_map_lookup_elem(), the verifier prevents eBPF programs from accessing beyond map->value_size through check_map_access(). Also from syscall side map_lookup_elem() only copies map->value_size back to user, so nothing could leak. [1] http://github.com/google/syzkaller Fixes: 28fbcfa08d8e ("bpf: add array type of eBPF maps") Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/bpf/arraymap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 8a6616583f38..1c1b8ab34037 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -109,7 +109,7 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
/* all elements already exist */
return -EEXIST;
- memcpy(array->value + array->elem_size * index, value, array->elem_size);
+ memcpy(array->value + array->elem_size * index, value, map->value_size);
return 0;
}