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Date: Thu, 25 Feb 2010 16:42:11 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: LKML <linux-kernel@...r.kernel.org> cc: Ingo Molnar <mingo@...e.hu>, Jesse Barnes <jbarnes@...tuousgeek.org>, Yinghai Lu <yinghai@...nel.org>, Bjorn Helgaas <bjorn.helgaas@...com> 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@...e.hu> Signed-off-by: Thomas Gleixner <tglx@...utronix.de> Cc: Bjorn Helgaas <bjorn.helgaas@...com> Cc: Yinghai Lu <yinghai@...nel.org> Cc: Jesse Barnes <jbarnes@...tuousgeek.org> Cc: stable@...nel.org --- arch/x86/pci/mmconfig-shared.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) Index: linux-2.6/arch/x86/pci/mmconfig-shared.c =================================================================== --- linux-2.6.orig/arch/x86/pci/mmconfig-shared.c +++ linux-2.6/arch/x86/pci/mmconfig-shared.c @@ -303,22 +303,17 @@ static void __init pci_mmcfg_check_end_b { 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; } } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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