From 15261678a8c2ff093ffedad730b1646d34a1716a Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Mon, 30 Jan 2023 23:53:52 -0500
Subject: [PATCH] parisc: fix livelock in uaccess
parisc 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.
Tested-by: Helge Deller <deller@gmx.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/parisc/mm/fault.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 869204e97ec9d..6941fdbf25173 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -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)
--
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