• Juntong Deng's avatar
    bpf: Make the pointer returned by iter next method valid · 4cc8c50c
    Juntong Deng authored
    Currently we cannot pass the pointer returned by iter next method as
    argument to KF_TRUSTED_ARGS or KF_RCU kfuncs, because the pointer
    returned by iter next method is not "valid".
    
    This patch sets the pointer returned by iter next method to be valid.
    
    This is based on the fact that if the iterator is implemented correctly,
    then the pointer returned from the iter next method should be valid.
    
    This does not make NULL pointer valid. If the iter next method has
    KF_RET_NULL flag, then the verifier will ask the ebpf program to
    check NULL pointer.
    
    KF_RCU_PROTECTED iterator is a special case, the pointer returned by
    iter next method should only be valid within RCU critical section,
    so it should be with MEM_RCU, not PTR_TRUSTED.
    
    Another special case is bpf_iter_num_next, which returns a pointer with
    base type PTR_TO_MEM. PTR_TO_MEM should not be combined with type flag
    PTR_TRUSTED (PTR_TO_MEM already means the pointer is valid).
    
    The pointer returned by iter next method of other types of iterators
    is with PTR_TRUSTED.
    
    In addition, this patch adds get_iter_from_state to help us get the
    current iterator from the current state.
    Signed-off-by: default avatarJuntong Deng <juntong.deng@outlook.com>
    Link: https://lore.kernel.org/r/AM6PR03MB584869F8B448EA1C87B7CDA399962@AM6PR03MB5848.eurprd03.prod.outlook.comSigned-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    4cc8c50c
verifier.c 672 KB