[xen stable-4.15] pci: fix handling of PCI bridges with subordinate bus number 0xff

[patchbot@xxxxxxx]

commit d4f39cf717539e9455a2b83321e05db37171f855
Author:     Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
AuthorDate: Fri Oct 15 11:04:46 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Oct 15 11:04:46 2021 +0200

    pci: fix handling of PCI bridges with subordinate bus number 0xff
    
    Bus number 0xff is valid according to the PCI spec. Using u8 typed sub_bus
    and assigning 0xff to it will result in the following loop getting stuck.
    
        for ( ; sec_bus <= sub_bus; sec_bus++ ) {...}
    
    Just change its type to unsigned int similarly to what is already done in
    dmar_scope_add_buses().
    
    Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
    master commit: 9c3b9800e2019c93ab22da69e4a0b22d6fb059ec
    master date: 2021-09-28 16:04:50 +0200
---
 xen/drivers/passthrough/pci.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index a9e3ac906f..e2c022aeea 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -363,8 +363,7 @@ static struct pci_dev *alloc_pdev(struct pci_seg *pseg, u8 
bus, u8 devfn)
     /* update bus2bridge */
     switch ( pdev->type = pdev_type(pseg->nr, bus, devfn) )
     {
-        u16 cap;
-        u8 sec_bus, sub_bus;
+        unsigned int cap, sec_bus, sub_bus;
 
         case DEV_TYPE_PCIe2PCI_BRIDGE:
         case DEV_TYPE_LEGACY_PCI_BRIDGE:
@@ -431,7 +430,7 @@ static void free_pdev(struct pci_seg *pseg, struct pci_dev 
*pdev)
     /* update bus2bridge */
     switch ( pdev->type )
     {
-        uint8_t sec_bus, sub_bus;
+        unsigned int sec_bus, sub_bus;
 
         case DEV_TYPE_PCIe2PCI_BRIDGE:
         case DEV_TYPE_LEGACY_PCI_BRIDGE:
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.15