info: Return dedicated error when program info is restricted #1858
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florianl
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ti-mo
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On systems where the `kernel.kptr_restrict` and `net.core.bpf_jit_harden` sysctls are enabled, certain fields in the program info may be restricted. When this is the case xlated and jitted instruction, line info, and function info are unavailable. When such fields are unavailable, we do get ..len fields set to non-zero values, but the kernel will have not written any data to the pointers provided. At present when this happens we don't recognize this and attempt to parse the empty buffers resulting in a `parse func info: offset 0: type ID 0 is a *btf.Void, but expected a Func` error. The only clue we have that this is happening is that the kernel will zero out the insns pointer. This commit adds logic to detect when this happens and then returns a dedicated `ErrInfoRestricted` error so this case can be handled gracefully. Signed-off-by: Dylan Reimerink <[email protected]>
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On systems where the
kernel.kptr_restrictandnet.core.bpf_jit_hardensysctls are enabled, certain fields in the program info may be restricted. When this is the case xlated and jitted instruction, line info, and function info are unavailable.When such fields are unavailable, we do get ..len fields set to non-zero values, but the kernel will have not written any data to the pointers provided. Link
At present when this happens we don't recognize this and attempt to parse the empty buffers resulting in a
parse func info: offset 0: type ID 0 is a *btf.Void, but expected a Funcerror.The only clue we have that this is happening is that the kernel will zero out the insns pointer. This commit adds logic to detect when this happens and then returns a dedicated
ErrInfoRestrictederror so this case can be handled gracefully.This is similar to / based on the approach bpftool has taken to handle this.