basic: Fix capability_ambient_set_apply for kernels < 4.3 #15246
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systemd#14133 made capability_ambient_set_apply() acquire capabilities that were explicitly asked for and drop all others. This change means the function is called even with an empty capability set, opening up a code path for users without ambient capabilities to call this function. This function will error with EINVAL out on kernels < 4.3 because PR_CAP_AMBIENT is not understood. This turns capability_ambient_set_apply() into a noop for kernels < 4.3 Fixes systemd#15225
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uh, i don't think setting ambient caps should be a NOP on old kernels. what#s the rationale here? i don't follow? i mean, I think it's fine to ignore caps the underlying kernel doesn't know, for compat reasons. i also think it's ok to ignore caps not in our own bounding set (since apparently they were made unavailable to us as a whole and we probably should accept that), but if a cap is defined and we have it but cannot pass it, that should be an error condition, and this issue breaks that, no? what am I missing? @keur can you elaborate? |
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#14133 made
capability_ambient_set_apply() acquire capabilities that were explicitly
asked for and drop all others. This change means the function is called
even with an empty capability set, opening up a code path for users
without ambient capabilities to call this function. This function will
error with EINVAL out on kernels < 4.3 because PR_CAP_AMBIENT is not
understood. This turns capability_ambient_set_apply() into a noop for
kernels < 4.3
Fixes #15225