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authorDaniel Borkmann <daniel@iogearbox.net>2015-11-30 13:02:56 +0100
committerDavid S. Miller <davem@davemloft.net>2015-12-01 21:56:17 -0500
commitfbca9d2d35c6ef1b323fae75cc9545005ba25097 (patch)
treeb2f43df7ab3851576874631536b3f20f0d5d4911 /kernel/bpf
parentceb5d58b217098a657f3850b7a2640f995032e62 (diff)
downloadlinux-sh-fbca9d2d35c6ef1b323fae75cc9545005ba25097.tar.gz
bpf, array: fix heap out-of-bounds access when updating elements
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>
Diffstat (limited to 'kernel/bpf')
-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 3f4c99e06c6b..4c67ce39732e 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -105,7 +105,7 @@ 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;
}