Daniel Borkmann fbca9d2d35 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 1be7f75d16 ("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: 28fbcfa08d ("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>		2015-12-01 21:56:17 -05:00
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arraymap.c	bpf, array: fix heap out-of-bounds access when updating elements	2015-12-01 21:56:17 -05:00
core.c	bpf: consolidate bpf_prog_put{, _rcu} dismantle paths	2015-11-02 22:48:39 -05:00
hashtab.c	bpf: convert hashtab lock to raw lock	2015-11-02 15:45:43 -05:00
helpers.c	bpf: split state from prandom_u32() and consolidate {c, e}BPF prngs	2015-10-08 05:26:39 -07:00
inode.c	bpf: fix clearing on persistent program array maps	2015-11-25 12:14:09 -05:00
Makefile	bpf: add support for persistent maps/progs	2015-11-02 22:48:39 -05:00
syscall.c	bpf: fix clearing on persistent program array maps	2015-11-25 12:14:09 -05:00
verifier.c	bpf: fix clearing on persistent program array maps	2015-11-25 12:14:09 -05:00