x86: Barf when vmalloc and kmemcheck faults happen in NMI (ebc8827f) · Commits · 戴 / test

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 <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>

arch/x86/mm/fault.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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

arch/x86/mm/kmemcheck/kmemcheck.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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

Admin message