[PATCH 02/10] hexagon: fix livelock in uaccess

Al Viro
2023-01-31T20:04:04Z

hexagon 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>
---
arch/hexagon/mm/vm_fault.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/hexagon/mm/vm_fault.c b/arch/hexagon/mm/vm_fault.c
index f73c7cbfe326..4b578d02fd01 100644
--- a/arch/hexagon/mm/vm_fault.c
+++ b/arch/hexagon/mm/vm_fault.c
@@ -93,8 +93,11 @@ void do_page_fault(unsigned long address, long cause, 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 (!user_mode(regs))
+ goto no_context;
return;
+ }

/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED)
--
2.30.2