From dce45493aff3fdd57fed2a0da264e585dba88433 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 30 Jan 2023 23:34:16 -0500 Subject: [PATCH] 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 --- arch/alpha/mm/fault.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/alpha/mm/fault.c b/arch/alpha/mm/fault.c index ef427a6..7b01ae4 100644 --- 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) -- 2.7.4