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Jesper Dangaard Brouer authored
The bpf infrastructure and verifier goes to great length to avoid bpf progs leaking kernel (pointer) info. For queueing an xdp_buff via XDP_REDIRECT, xdp_frame info stores kernel info (incl pointers) in top part of frame data (xdp->data_hard_start). Checks are in place to assure enough headroom is available for this. This info is not cleared, and if the frame is reused, then a malicious user could use bpf_xdp_adjust_head helper to move xdp->data into this area. Thus, making this area readable. This is not super critical as XDP progs requires root or CAP_SYS_ADMIN, which are privileged enough for such info. An effort (is underway) towards moving networking bpf hooks to the lesser privileged mode CAP_NET_ADMIN, where leaking such info should be avoided. Thus, this patch to clear the info when needed. Signed-off-by:
Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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