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authorSteven Rostedt <srostedt@redhat.com>2009-02-19 11:46:36 -0500
committerSteven Rostedt <srostedt@redhat.com>2009-02-20 11:44:47 -0500
commit3c3e5694add02e665bbbd0fecfbbdcc0b903097a (patch)
tree949dd1e8f6f5903bedf3e20b407da1b4d2823881 /arch/x86/mm
parent07a66d7c53a538e1a9759954a82bb6c07365eff9 (diff)
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@redhat.com>
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/fault.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index c76ef1d701c..278d645d108 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;
}
/*