Commit 15261678 authored Jan 30, 2023 by Al Viro

parisc: fix livelock in uaccess

parisc equivalent of 26178ec1 "x86: mm: consolidate VM_FAULT_RETRY handling"
If e.g. get_user() triggers a page fault and a fatal signal is caught, we might
end up with handle_mm_fault() returning VM_FAULT_RETRY and not doing anything
to page tables. In such case we must *not* return to the faulting insn -
that would repeat the entire thing without making any progress; what we need
instead is to treat that as failed (user) memory access.

Tested-by: Helge Deller <deller@gmx.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent 0b92ed09

arch/parisc/mm/fault.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -308,8 +308,13 @@ void do_page_fault(struct pt_regs *regs, unsigned long code,

		fault = handle_mm_fault(vma, address, flags, regs);

		if (fault_signal_pending(fault, regs))
		if (fault_signal_pending(fault, regs)) {
		if (!user_mode(regs)) {
		msg = "Page fault: fault signal on kernel memory";
		goto no_context;
		}
		return;
		}

		/* The fault is fully completed (including releasing mmap lock) */
		if (fault & VM_FAULT_COMPLETED)