alpha: fix livelock in uaccess

alpha equivalent of 26178ec11ef3 "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>

diff --git a/arch/alpha/mm/fault.c b/arch/alpha/mm/fault.c
index ef427a6bdd1ab91be0445b0261d38bb49bb2be93..7b01ae4f3bc6c7ab53dfb0c219c6fd75e2ffdf36 100644 (file)
--- a/arch/alpha/mm/fault.c
+++ b/arch/alpha/mm/fault.c
@@ -152,8 +152,11 @@ retry:
           the fault.  */
        fault = handle_mm_fault(vma, address, flags, regs);
 
-       if (fault_signal_pending(fault, regs))
+       if (fault_signal_pending(fault, regs)) {
+               if (!user_mode(regs))
+                       goto no_context;
                return;
+       }
 
        /* The fault is fully completed (including releasing mmap lock) */
        if (fault & VM_FAULT_COMPLETED)