Why does do_syscal_user_dispatch call do_exit(SIGSEGV) and do_exit(SIGSYS) instead of force_sig(SIGSEGV) and force_sig(SIGSYS)?
Looking at the code these cases are not expected to happen, so I would be surprised if userspace depends on any particular behaviour on the failure path so I think we can change this.
Is using do_exit in this way something you copied from seccomp?
The reason I am asking is that by using do_exit you deprive userspace of the change to catch the signal handler and try and fix things.
Also by using do_exit only a single thread of a multi-thread application is terminated which seems wrong.
I am asking because I am going through the callers of do_exit so I can refactor things and clean things up and this use just looks wrong.
Gabriel Krisman Bertazi krisman@collabora.com writes:
<snip>
+bool do_syscall_user_dispatch(struct pt_regs *regs) +{
- struct syscall_user_dispatch *sd = ¤t->syscall_dispatch;
- char state;
- if (likely(instruction_pointer(regs) - sd->offset < sd->len))
return false;- if (unlikely(arch_syscall_is_vdso_sigreturn(regs)))
return false;- if (likely(sd->selector)) {
/** access_ok() is performed once, at prctl time, when* the selector is loaded by userspace.*/if (unlikely(__get_user(state, sd->selector)))do_exit(SIGSEGV);
^^^^^^^^^^^^^^^^
I think it makes more sense if the code does:
if (unlikely(__get_user(state, sd->selector))) { force_sig(SIGSEGV); return true; }
if (likely(state == PR_SYS_DISPATCH_OFF))return false;if (state != PR_SYS_DISPATCH_ON)do_exit(SIGSYS);
^^^^^^^^^^^^^^^
- }
- sd->on_dispatch = true;
- syscall_rollback(current, regs);
- trigger_sigsys(regs);
- return true;
+}
Eric