Commit 79c54c97 authored Jan 31, 2023 by Al Viro

sparc: fix livelock in uaccess

sparc 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.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent dce45493

arch/sparc/mm/fault_32.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -187,8 +187,11 @@ asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
		*/
		fault = handle_mm_fault(vma, address, flags, regs);

		if (fault_signal_pending(fault, regs))
		if (fault_signal_pending(fault, regs)) {
		if (!from_user)
		goto no_context;
		return;
		}

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

arch/sparc/mm/fault_64.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -424,8 +424,13 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)

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

		if (fault_signal_pending(fault, regs))
		if (fault_signal_pending(fault, regs)) {
		if (regs->tstate & TSTATE_PRIV) {
		insn = get_fault_insn(regs, insn);
		goto handle_kernel_fault;
		}
		goto exit_exception;
		}

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