diff options
| author | Steven Rostedt <srostedt@redhat.com> | 2009-02-19 11:46:36 -0500 |
|---|---|---|
| committer | Steven Rostedt <srostedt@redhat.com> | 2009-02-20 11:44:47 -0500 |
| commit | 3c3e5694add02e665bbbd0fecfbbdcc0b903097a (patch) | |
| tree | 949dd1e8f6f5903bedf3e20b407da1b4d2823881 /arch/x86/mm | |
| parent | 07a66d7c53a538e1a9759954a82bb6c07365eff9 (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.c | 13 |
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; } /* |