Andy Lutomirski luto@kernel.org writes:
On Thu, Jul 16, 2020 at 12:31 PM Gabriel Krisman Bertazi krisman@collabora.com wrote:
This is quite nice. I have a few comments, though:
You mentioned rt_sigreturn(). Should this automatically exempt the kernel-provided signal restorer on architectures (e.g. x86_32) that provide one?
That seems reasonable. Not sure how easy it is to do it, though.
The amount of syscall entry wiring that arches need to do is IMO already a bit out of hand. Should we instead rename TIF_SECCOMP to TIF_SYSCALL_INTERCEPTION and have one generic callback that handles seccomp and this new thing?
Considering the previous suggestion from Kees to hide it inside the tracehook and Thomas rework of this path, I'm not sure what is the best solution here, but some rework of these flags is due. Thomas suggested expanding these flags to 64 bits and having some arch specific and arch-agnostic flags. With the storage expansion and arch-agnostic flags, would this still be desirable?
+int do_syscall_user_dispatch(struct pt_regs *regs) +{
struct syscall_user_dispatch *sd = ¤t->syscall_dispatch;unsigned long ip = instruction_pointer(regs);char state;if (likely(ip >= sd->dispatcher_start && ip <= sd->dispatcher_end))return 0;if (likely(sd->selector)) {if (unlikely(__get_user(state, sd->selector)))do_exit(SIGSEGV);if (likely(state == 0))return 0;if (state != 1)do_exit(SIGSEGV);This seems a bit extreme and hard to debug if it ever happens.
Makes sense, but I don't see a better way to return the error here. Maybe a SIGSYS with a different si_errno? Alternatively, we could revert to the previous behavior of allowing syscalls on state != 0, that existed in v1. What do you think?