diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c index ffacb87be29d..4216fd3f5d34 100644 --- a/sys/amd64/amd64/trap.c +++ b/sys/amd64/amd64/trap.c @@ -972,4 +972,21 @@ amd64_syscall(struct thread *td, int traced) syscallname(td->td_proc, sa.code))); syscallret(td, error, &sa); + + /* + * If the user-supplied value of %rip is not a canonical + * address, then some CPUs will trigger a ring 0 #GP during + * the sysret instruction. However, the fault handler would + * execute with the user's %gs and %rsp in ring 0 which would + * not be safe. Instead, preemptively kill the thread with a + * SIGBUS. + */ + if (td->td_frame->tf_rip >= VM_MAXUSER_ADDRESS) { + ksiginfo_init_trap(&ksi); + ksi.ksi_signo = SIGBUS; + ksi.ksi_code = BUS_OBJERR; + ksi.ksi_trapno = T_PROTFLT; + ksi.ksi_addr = (void *)td->td_frame->tf_rip; + trapsignal(td, &ksi); + } }