From: Thomas Bogendoerfer Date: Thu, 21 Jan 2021 16:04:16 +0000 (+0100) Subject: MIPS: mm: abort uaccess retries upon fatal signal X-Git-Tag: accepted/tizen/unified/20230118.172025~7732^2~68 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=fceb90bb43ca5c01eff73367f71a76c06f049b41;p=platform%2Fkernel%2Flinux-rpi.git MIPS: mm: abort uaccess retries upon fatal signal When there's a fatal signal pending, MIPS's do_page_fault() implementation returns. The intent is that we'll return to the faulting userspace instruction, delivering the signal on the way. However, if we take a fatal signal during fixing up a uaccess, this results in a return to the faulting kernel instruction, which will be instantly retried, resulting in the same fault being taken forever. As the task never reaches userspace, the signal is not delivered, and the task is left unkillable. While the task is stuck in this state, it can inhibit the forward progress of the system. To avoid this, we must ensure that when a fatal signal is pending, we apply any necessary fixup for a faulting kernel instruction. Thus we will return to an error path, and it is up to that code to make forward progress towards delivering the fatal signal. [ Description taken from commit 746a272e4414 ("ARM: 8692/1: mm: abort uaccess retries upon fatal signal") ] Signed-off-by: Thomas Bogendoerfer Acked-by: Mark Rutland --- diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c index 7c871b1..e7abda9 100644 --- a/arch/mips/mm/fault.c +++ b/arch/mips/mm/fault.c @@ -156,8 +156,11 @@ good_area: */ 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; + } if (unlikely(fault & VM_FAULT_ERROR)) { if (fault & VM_FAULT_OOM)