path: root/kernel/bpf/helpers.c
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authorDaniel Borkmann <>2016-04-13 00:10:51 +0200
committerDavid S. Miller <>2016-04-14 21:40:41 -0400
commit435faee1aae9c1ac231f89e4faf0437bfe29f425 (patch)
treec22bae0b4ec5888b423eb8a8548d88bbf4586def /kernel/bpf/helpers.c
parent33ff9823c569f3aceb071071914919177a6bed6a (diff)
bpf, verifier: add ARG_PTR_TO_RAW_STACK type
When passing buffers from eBPF stack space into a helper function, we have ARG_PTR_TO_STACK argument type for helpers available. The verifier makes sure that such buffers are initialized, within boundaries, etc. However, the downside with this is that we have a couple of helper functions such as bpf_skb_load_bytes() that fill out the passed buffer in the expected success case anyway, so zero initializing them prior to the helper call is unneeded/wasted instructions in the eBPF program that can be avoided. Therefore, add a new helper function argument type called ARG_PTR_TO_RAW_STACK. The idea is to skip the STACK_MISC check in check_stack_boundary() and color the related stack slots as STACK_MISC after we checked all call arguments. Helper functions using ARG_PTR_TO_RAW_STACK must make sure that every path of the helper function will fill the provided buffer area, so that we cannot leak any uninitialized stack memory. This f.e. means that error paths need to memset() the buffers, but the expected fast-path doesn't have to do this anymore. Since there's no such helper needing more than at most one ARG_PTR_TO_RAW_STACK argument, we can keep it simple and don't need to check for multiple areas. Should in future such a use-case really appear, we have check_raw_mode() that will make sure we implement support for it first. Signed-off-by: Daniel Borkmann <> Acked-by: Alexei Starovoitov <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'kernel/bpf/helpers.c')
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