The underlying lookup_user_key() function uses a signed 32 bit integer for key serial numbers because legitimate serial numbers are positive (and > 3) and keyrings are negative. Using a u32 for the keyring in the bpf function doesn't currently cause any conversion problems but will start to trip the signed to unsigned conversion warnings when the kernel enables them, so convert the argument to signed (and update the tests accordingly) before it acquires more users. Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com> Link: https://lore.kernel.org/r/84cdb0775254d297d75e21f577089f64abdfbd28.camel@HansenPartnership.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>