PCI: Prevent restoring assigned resources

restore_dev_resource() copies saved addresses and flags from the struct
pci_dev_resource back to the struct resource, typically, during rollback
from a failure or in preparation for a retry attempt.

If the resource is within resource tree, the resource must not be
modified as the resource tree could be corrupted. Thus, it's a bug to
call restore_dev_resource() for assigned resources (which did happen
due to logic flaws in the BAR resize rollback).

Add WARN_ON_ONCE() into restore_dev_resource() to detect such bugs easily
and return without altering the resource to prevent corruption.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Alex Bennée <alex.bennee@linaro.org> # AVA, AMD GPU
Link: https://patch.msgid.link/20251113162628.5946-12-ilpo.jarvinen@linux.intel.com

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 7e268960954bdfc2c2409aa909837b76fe37a248..1d9fc078c7adff64c00b7315b36ade80e5d7c14a 100644 (file)
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -15,6 +15,7 @@
  */
 
 #include <linux/bitops.h>
+#include <linux/bug.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -135,6 +136,9 @@ static void restore_dev_resource(struct pci_dev_resource *dev_res)
 {
        struct resource *res = dev_res->res;
 
+       if (WARN_ON_ONCE(res->parent))
+               return;
+
        res->start = dev_res->start;
        res->end = dev_res->end;
        res->flags = dev_res->flags;