From ebc8827f75954fe315492883eee5cb3f355d547d Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 27 Sep 2010 18:50:51 +0200 Subject: [PATCH] x86: Barf when vmalloc and kmemcheck faults happen in NMI In x86, faults exit by executing the iret instruction, which then reenables NMIs if we faulted in NMI context. Then if a fault happens in NMI, another NMI can nest after the fault exits. But we don't yet support nested NMIs because we have only one NMI stack. To prevent from that, check that vmalloc and kmemcheck faults don't happen in this context. Most of the other kernel faults in NMIs can be more easily spotted by finding explicit copy_from,to_user() calls on review. Signed-off-by: Frederic Weisbecker Cc: Ingo Molnar Cc: Thomas Gleixner Cc: H. Peter Anvin Cc: Mathieu Desnoyers Cc: Peter Zijlstra --- arch/x86/mm/fault.c | 4 ++++ arch/x86/mm/kmemcheck/kmemcheck.c | 2 ++ 2 files changed, 6 insertions(+) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 4c4508e..a24c6cf 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -251,6 +251,8 @@ static noinline __kprobes int vmalloc_fault(unsigned long address) if (!(address >= VMALLOC_START && address < VMALLOC_END)) return -1; + WARN_ON_ONCE(in_nmi()); + /* * Synchronize this task's top level page-table * with the 'reference' page table. @@ -369,6 +371,8 @@ static noinline __kprobes int vmalloc_fault(unsigned long address) if (!(address >= VMALLOC_START && address < VMALLOC_END)) return -1; + WARN_ON_ONCE(in_nmi()); + /* * Copy kernel mappings over when needed. This can also * happen within a race in page table update. In the later diff --git a/arch/x86/mm/kmemcheck/kmemcheck.c b/arch/x86/mm/kmemcheck/kmemcheck.c index b3b531a..d87dd6d 100644 --- a/arch/x86/mm/kmemcheck/kmemcheck.c +++ b/arch/x86/mm/kmemcheck/kmemcheck.c @@ -631,6 +631,8 @@ bool kmemcheck_fault(struct pt_regs *regs, unsigned long address, if (!pte) return false; + WARN_ON_ONCE(in_nmi()); + if (error_code & 2) kmemcheck_access(regs, address, KMEMCHECK_WRITE); else -- 2.7.4