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x86/PCI: Prevent mmconfig memory corruption

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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>
This commit is contained in:
Thomas Gleixner 2010-02-25 16:42:11 +01:00 committed by Jesse Barnes
parent cbbc0de700
commit bb8d41330c
1 changed files with 6 additions and 11 deletions
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17
arch/x86/pci/mmconfig-shared.c
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@ -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;
}
}