On 02/23/2019 12:38 PM, Alexei Starovoitov wrote:
> On Sat, Feb 23, 2019 at 11:07:09AM -0800, Eric Dumazet wrote:
>> If caller of bpf_setsockopt() is silly passing a negative optlen
>> bad things happen.
>>
>> Fixes: 91b5b21c7c16 ("bpf: Add support for changing congestion control")
>> Signed-off-by: Eric Dumazet <eduma...@google.com>
>> Cc: Lawrence Brakmo <bra...@fb.com>
>> ---
>> net/core/filter.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/core/filter.c b/net/core/filter.c
>> index
>> f7d0004fc16096eb42ece3a6acf645540ee2326b..6a5d89464168f2f35f43986c1dbc0446c9390a3c
>> 100644
>> --- a/net/core/filter.c
>> +++ b/net/core/filter.c
>> @@ -4194,8 +4194,9 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *,
>> bpf_sock,
>> char name[TCP_CA_NAME_MAX];
>> bool reinit = bpf_sock->op > BPF_SOCK_OPS_NEEDS_ECN;
>>
>> - strncpy(name, optval, min_t(long, optlen,
>> - TCP_CA_NAME_MAX-1));
>> + if (optlen < 0)
>> + return -EINVAL;
>> + strncpy(name, optval, min(optlen, TCP_CA_NAME_MAX - 1));
>
> Unnecessary.
> The verifier guarantees that optlen > 0 because
> static const struct bpf_func_proto bpf_setsockopt_proto = {
> .func = bpf_setsockopt,
> ...
> .arg5_type = ARG_CONST_SIZE,
> };
>
Even on 32bit kernel ?
The suspect thing to me is the min_t(long, ....)
optlen is an integer, why do we need to promote to a long ?
