On Thu, Apr 12, 2012 at 2:47 PM, Will Drewry <wad@xxxxxxxxxxxx> wrote: > From: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > > With this change, calling > prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) > disables privilege granting operations at execve-time. For example, a > process will not be able to execute a setuid binary to change their uid > or gid if this bit is set. The same is true for file capabilities. > > Additionally, LSM_UNSAFE_NO_NEW_PRIVS is defined to ensure that > LSMs respect the requested behavior. > > To determine if the NO_NEW_PRIVS bit is set, a task may call > prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0); > It returns 1 if set and 0 if it is not set. If any of the arguments are > non-zero, it will return -1 and set errno to -EINVAL. > (PR_SET_NO_NEW_PRIVS behaves similarly.) > > This functionality is desired for the proposed seccomp filter patch > series. By using PR_SET_NO_NEW_PRIVS, it allows a task to modify the > system call behavior for itself and its child tasks without being > able to impact the behavior of a more privileged task. > > Another potential use is making certain privileged operations > unprivileged. For example, chroot may be considered "safe" if it cannot > affect privileged tasks. > > Note, this patch causes execve to fail when PR_SET_NO_NEW_PRIVS is > set and AppArmor is in use. It is fixed in a subsequent patch. > > Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Signed-off-by: Will Drewry <wad@xxxxxxxxxxxx> > Acked-by: Eric Paris <eparis@xxxxxxxxxx> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook ChromeOS Security -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
