Author: Steven Rostedt <srostedt@xxxxxxxxxx> AuthorDate: Thu, 19 Feb 2009 11:46:36 -0500 Commit: Steven Rostedt <srostedt@xxxxxxxxxx> CommitDate: Fri, 20 Feb 2009 11:44:47 -0500 x86: check PMD in spurious_fault handler Impact: fix to prevent hard lockup on bad PMD permissions If the PMD does not have the correct permissions for a page access, but the PTE does, the spurious fault handler will mistake the fault as a lazy TLB transaction. This will result in an infinite loop of: fault -> spurious_fault check (pass) -> return to code -> fault This patch adds a check and a warn on if the PTE passes the permissions but the PMD does not. [ Updated: Ingo Molnar suggested using WARN_ONCE with some text ] Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx> --- arch/x86/mm/fault.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index c76ef1d..278d645 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -455,6 +455,7 @@ static int spurious_fault(unsigned long address, pud_t *pud; pmd_t *pmd; pte_t *pte; + int ret; /* Reserved-bit violation or user access to kernel space? */ if (error_code & (PF_USER | PF_RSVD)) @@ -482,7 +483,17 @@ static int spurious_fault(unsigned long address, if (!pte_present(*pte)) return 0; - return spurious_fault_check(error_code, pte); + ret = spurious_fault_check(error_code, pte); + if (!ret) + return 0; + + /* + * Make sure we have permissions in PMD + * If not, then there's a bug in the page tables. + */ + ret = spurious_fault_check(error_code, (pte_t *) pmd); + WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); + return ret; } /* -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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