From bb8d41330ce27edb91adb6922d3f8e1a8923f727 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 25 Feb 2010 16:42:11 +0100
Subject: [PATCH] x86/PCI: Prevent mmconfig memory corruption
commit ff097ddd4 (x86/PCI: MMCONFIG: manage pci_mmcfg_region as a
list, not a table) introduced a nasty memory corruption when
pci_mmcfg_list is empty.
pci_mmcfg_check_end_bus_number() dereferences pci_mmcfg_list.prev even
when the list is empty. The following write hits some variable near to
pci_mmcfg_list.
Further down a similar problem exists, where cfg->list.next is
dereferenced unconditionally and a comparison with some variable near
to pci_mmcfg_list happens.
Add a check for the last element into the for_each_entry() loop and
remove all the other crappy logic which is just a leftover of the old
array based code which was replaced by the list conversion.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
---
arch/x86/pci/mmconfig-shared.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
index b19d1e54201ee9..8f3f9a50b1e0b4 100644
--- a/arch/x86/pci/mmconfig-shared.c
+++ b/arch/x86/pci/mmconfig-shared.c
@@ -303,22 +303,17 @@ static void __init pci_mmcfg_check_end_bus_number(void)
{
struct pci_mmcfg_region *cfg, *cfgx;
- /* last one*/
- cfg = list_entry(pci_mmcfg_list.prev, typeof(*cfg), list);
- if (cfg)
- if (cfg->end_bus < cfg->start_bus)
- cfg->end_bus = 255;
-
- if (list_is_singular(&pci_mmcfg_list))
- return;
-
- /* don't overlap please */
+ /* Fixup overlaps */
list_for_each_entry(cfg, &pci_mmcfg_list, list) {
if (cfg->end_bus < cfg->start_bus)
cfg->end_bus = 255;
+ /* Don't access the list head ! */
+ if (cfg->list.next == &pci_mmcfg_list)
+ break;
+
cfgx = list_entry(cfg->list.next, typeof(*cfg), list);
- if (cfg != cfgx && cfg->end_bus >= cfgx->start_bus)
+ if (cfg->end_bus >= cfgx->start_bus)
cfg->end_bus = cfgx->start_bus - 1;
}
}
--
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