Commits

Daniel Thompson committed a818777d424
libbb: Enable support for !CONFIG_MULTIUSER Linux recently gained a new config option, CONFIG_MULTIUSER, that makes support for non-root users optional. This results in a number of syscalls being disabled: setuid, setregid, setgid, setreuid, setresuid, getresuid, setresgid, getresgid, setgroups, getgroups, setfsuid, setfsgid, capget, capset. Currently a number of busybox applets, including login, struggle to run when CONFIG_MULTIUSER is disabled. Even the root user is unable to login: login: can't set groups: Functi This patch adds code to make change_identity() a nop on single user systems. It works by recognising the signature errno value (ENOSYS, due to the system calls being disabled) and, to avoid security risks, only deploys when the current uid and target uid is the same. After the patch is applied any attempt to switch to a non-root user will fail. Thus a badly configured userspace (for example, one that tries to start a daemon as a non-root user when the kernel cannot support this) will report errors as one would expect. Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>