Bug 220010

792bd08a41bdc309e08ff4d429f670cbb30f2b63 is stable tree commit-id

commit 792bd08a41bdc309e08ff4d429f670cbb30f2b63
Author: Nishanth Aravamudan <naravamudan@nvidia.com>
Date:   Fri Feb 7 14:56:00 2025 -0600

    PCI: Avoid reset when disabled via sysfs
    
    [ Upstream commit 479380efe1625e251008d24b2810283db60d6fcd ]
    
    After d88f521da3ef ("PCI: Allow userspace to query and set device reset
    mechanism"), userspace can disable reset of specific PCI devices by writing
    an empty string to the sysfs reset_method file.
    
    However, pci_slot_resettable() does not check pci_reset_supported(), which
    means that pci_reset_function() will still reset the device even if
    userspace has disabled all the reset methods.
    
    I was able to reproduce this issue with a vfio device passed to a qemu
    guest, where I had disabled PCI reset via sysfs.
    
    Add an explicit check of pci_reset_supported() in both
    pci_slot_resettable() and pci_bus_resettable() to ensure both the reset
    status and reset execution are bypassed if an administrator disables it for
    a device.
    
    Link: https://lore.kernel.org/r/20250207205600.1846178-1-naravamudan@nvidia.com
    Fixes: d88f521da3ef ("PCI: Allow userspace to query and set device reset mechanism")
    Signed-off-by: Nishanth Aravamudan <naravamudan@nvidia.com>
    [bhelgaas: commit log]
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
    Cc: Alex Williamson <alex.williamson@redhat.com>
    Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
    Cc: Amey Narkhede <ameynarkhede03@gmail.com>
    Cc: Jason Gunthorpe <jgg@nvidia.com>
    Cc: Yishai Hadas <yishaih@nvidia.com>
    Cc: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
    Cc: Kevin Tian <kevin.tian@intel.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 23609dd123f9..3e78cf86ef03 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5413,6 +5413,8 @@ static bool pci_bus_resettable(struct pci_bus *bus)
                return false;
 
        list_for_each_entry(dev, &bus->devices, bus_list) {
+               if (!pci_reset_supported(dev))
+                       return false;
                if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET ||
                    (dev->subordinate && !pci_bus_resettable(dev->subordinate)))
                        return false;
@@ -5489,6 +5491,8 @@ static bool pci_slot_resettable(struct pci_slot *slot)
        list_for_each_entry(dev, &slot->bus->devices, bus_list) {
                if (!dev->slot || dev->slot != slot)
                        continue;
+               if (!pci_reset_supported(dev))
+                       return false;
                if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET ||
                    (dev->subordinate && !pci_bus_resettable(dev->subordinate)))
                        return false;

Created attachment 307959 [details]
dmesg_1.log

dmesg_1.log: 03:00.0 and 03:00.1

Created attachment 307960 [details]
dmesg_2.log

dmesg_2.log: 03:00.0 only

Created attachment 307961 [details]
dmesg_3.log

dmesg_3.log: 792bd08a41bdc309e08ff4d429f670cbb30f2b63 reverted

Thanks for the report and sorry for the trouble.  Fix queued for v6.16: https://git.kernel.org/cgit/linux/kernel/git/pci/pci.git/commit/?id=bc0b828ef6e5

I added you as another reporter and included a link to this bugzilla.

Thanks for the support. I shall mark this as resolved.