bpf: simplify verifier register state assignments
authorAlexei Starovoitov <ast@fb.com>
Thu, 7 Apr 2016 02:39:21 +0000 (19:39 -0700)
committerDavid S. Miller <davem@davemloft.net>
Mon, 11 Apr 2016 02:43:18 +0000 (22:43 -0400)
commit4923ec0b10d998349c2ac4b38aa4674e539e6f92
treeaabed2c261f40d5c2010493b3ed9a9088aa5f7a9
parentae95d7126104591348d37aaf78c8325967e02386
bpf: simplify verifier register state assignments

verifier is using the following structure to track the state of registers:
struct reg_state {
    enum bpf_reg_type type;
    union {
        int imm;
        struct bpf_map *map_ptr;
    };
};
and later on in states_equal() does memcmp(&old->regs[i], &cur->regs[i],..)
to find equivalent states.
Throughout the code of verifier there are assignements to 'imm' and 'map_ptr'
fields and it's not obvious that most of the assignments into 'imm' don't
need to clear extra 4 bytes (like mark_reg_unknown_value() does) to make sure
that memcmp doesn't go over junk left from 'map_ptr' assignment.

Simplify the code by converting 'int' into 'long'

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
kernel/bpf/verifier.c