Messages in this thread | | | From | John Garry <> | Subject | [PATCH v3 0/4] Fix system crash for accessing unmapped IO port regions | Date | Thu, 4 Apr 2019 23:59:58 +0800 |
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It was reported some time ago that arm64 systems will crash if a driver attempts to access IO port addresses when the PCI IO port region has not been mapped [1].
More recently, a similar crash is where the system PCI host probe fails, and the IPMI driver crashes the system while attempting to do some IO port accesses [2].
This patchset attempts to keep the kernel alive in such situations by 2 complementary methods: 1. Rejecting IO port resource requests until PCI IO port regions have been mapped (in a pci_remap_iospace() call). 2. Rejecting logic PIO access to PCI IO regions until, again, PCI IO port regions have been mapped
About 1: Currently the PCI IO port region is initialized to the full range, {0, IO_SPACE_LIMIT}. As such, any IO port region requests would not fail because of PCI IO port regions not being mapped.
Patch 1/4 looks to remedy this issue by ensuring IO port requests are made to direct children of ioport_resource (PCI host IO port regions), similar to Arnd's solution, mentioned in [1]:
"I see that ioport_resource gets initialized to the {0, IO_SPACE_LIMIT} range. If we could change it so that pci_remap_iospace() hooks up to ioport_resource and extends it whenever something gets mapped there up to IO_SPACE_LIMIT, we can change the default range to {0,0}, which would fail for any request_region call before the first pci_remap_iospace."
I didn't use this solution, as logical PIO space is sparse in {0, IO_SPACE_LIMIT}, so we cannot simply grow the region.
*As discussed with Bjorn in v2 series, we doubt that this approach is sound, as legacy ISA devices do not necessarily reply on PCI.*
However I will keep the patch in the series as a reference and as a topic of debate.
It's also an RFC as the implementation solution is not idea.
About 2: Some drivers - like f71805f hwmon driver - do not call request_{muxed_}region() prior to accessing IO port regions, as they should do.
So patches 2-3/4 adds a safeguard against this, in that unwarranted PIO IO accesses will be discarded in the low-level accessors.
About the issue of f71805f driver not requesting the IO port region - many drivers do this, and need to be fixed up separately.
1. https://lore.kernel.org/linux-pci/56F209A9.4040304@huawei.com 2. https://lore.kernel.org/linux-arm-kernel/e6995b4a-184a-d8d4-f4d4-9ce75d8f47c0@huawei.com/
Differences to v2 patchset: https://lkml.org/lkml/2019/3/20/788 - Add a patch to use logical PIO accessors for !CONFIG_INDIRECT_PIO - Some tidy-up according to Andy's review
Differences to v1 patchset: https://lkml.org/lkml/2019/3/14/630 - Drop f71805f fix - it can be done in a separate patchset - Change implementation in resource.c patch to check if parent of region is ioport_resource - Add patch to fix some logic_pio.c prints
John Garry (4): resource: Request IO port regions from children of ioport_resource lib: logic_pio: Use logical PIO low-level accessors for !CONFIG_INDIRECT_PIO lib: logic_pio: Reject accesses to unregistered CPU MMIO regions lib: logic_pio: Fix up some prints
include/linux/ioport.h | 11 ++- include/linux/logic_pio.h | 7 +- kernel/resource.c | 28 +++++++ lib/logic_pio.c | 157 +++++++++++++++++++++++++++++--------- 4 files changed, 159 insertions(+), 44 deletions(-)
-- 2.17.1
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