[GIT pull] x86 fixes for 4.3

[GIT pull] x86 fixes for 4.3

[Thomas Gleixner]

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Linus,

please pull the latest x86-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-for-linus

This set of updates contains:

     - Another bugfix for the pathologic vm86 machinery. Clear
       thread.vm86 on fork to prevent corrupting the parent
       state. This comes along with an update to the vm86 selftest
       case

     - Fix another corner case in the ioapic setup code which causes
       a boot crash on some oddball systems

     - Fix the fallout from the dma allocation consolidation work,
       which leads to a NULL pointer dereference when the allocation
       code is called with a NULL device.

Thanks,

	tglx

------------------>
Andy Lutomirski (2):
      selftests/x86: Add a fork() to entry_from_vm86 to catch fork bugs
      x86/vm86: Set thread.vm86 to NULL on fork/clone

Ville Syrjälä (1):
      x86/dma-mapping: Fix arch_dma_alloc_attrs() oops with NULL dev

Werner Pawlitschko (1):
      x86/ioapic: Prevent NULL pointer dereference in setup_ioapic_dest()


 arch/x86/kernel/apic/io_apic.c                | 4 +++-
 arch/x86/kernel/pci-dma.c                     | 5 +++--
 arch/x86/kernel/process.c                     | 3 +++
 tools/testing/selftests/x86/entry_from_vm86.c | 4 ++++
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index bb6bfc01cb82..4f2821527014 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2547,7 +2547,9 @@ void __init setup_ioapic_dest(void)
 			mask = apic->target_cpus();
 
 		chip = irq_data_get_irq_chip(idata);
-		chip->irq_set_affinity(idata, mask, false);
+		/* Might be lapic_chip for irq 0 */
+		if (chip->irq_set_affinity)
+			chip->irq_set_affinity(idata, mask, false);
 	}
 }
 #endif
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 1b55de1267cf..cd99433b8ba1 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -131,11 +131,12 @@ void dma_generic_free_coherent(struct device *dev, size_t size, void *vaddr,
 
 bool arch_dma_alloc_attrs(struct device **dev, gfp_t *gfp)
 {
+	if (!*dev)
+		*dev = &x86_dma_fallback_dev;
+
 	*gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
 	*gfp = dma_alloc_coherent_gfp_flags(*dev, *gfp);
 
-	if (!*dev)
-		*dev = &x86_dma_fallback_dev;
 	if (!is_device_dma_capable(*dev))
 		return false;
 	return true;
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index e28db181e4fc..9f7c21c22477 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -84,6 +84,9 @@ EXPORT_SYMBOL_GPL(idle_notifier_unregister);
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 {
 	memcpy(dst, src, arch_task_struct_size);
+#ifdef CONFIG_VM86
+	dst->thread.vm86 = NULL;
+#endif
 
 	return fpu__copy(&dst->thread.fpu, &src->thread.fpu);
 }
diff --git a/tools/testing/selftests/x86/entry_from_vm86.c b/tools/testing/selftests/x86/entry_from_vm86.c
index 421c607a8856..d075ea0e5ca1 100644
--- a/tools/testing/selftests/x86/entry_from_vm86.c
+++ b/tools/testing/selftests/x86/entry_from_vm86.c
@@ -230,5 +230,9 @@ int main(void)
 	}
 	clearhandler(SIGSEGV);
 
+	/* Make sure nothing explodes if we fork. */
+	if (fork() > 0)
+		return 0;
+
 	return (nerrs == 0 ? 0 : 1);
 }

[GIT pull] x86 fixes for 4.3

[Thomas Gleixner]

Linus,

please pull the latest x86-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-for-linus

Two bugfixes from Andy addressing at least some of the subtle NMI
related wreckage which has been reported by Sasha Levin.

Thanks,

	tglx

------------------>
Andy Lutomirski (2):
      x86/paravirt: Replace the paravirt nop with a bona fide empty function
      x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code


 arch/x86/entry/entry_64.S  | 16 +++++++++++++++-
 arch/x86/kernel/paravirt.c | 16 ++++++++++++----
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index d3033183ed70..055a01de7c8d 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1128,7 +1128,18 @@ END(error_exit)
 
 /* Runs on exception stack */
 ENTRY(nmi)
+	/*
+	 * Fix up the exception frame if we're on Xen.
+	 * PARAVIRT_ADJUST_EXCEPTION_FRAME is guaranteed to push at most
+	 * one value to the stack on native, so it may clobber the rdx
+	 * scratch slot, but it won't clobber any of the important
+	 * slots past it.
+	 *
+	 * Xen is a different story, because the Xen frame itself overlaps
+	 * the "NMI executing" variable.
+	 */
 	PARAVIRT_ADJUST_EXCEPTION_FRAME
+
 	/*
 	 * We allow breakpoints in NMIs. If a breakpoint occurs, then
 	 * the iretq it performs will take us out of NMI context.
@@ -1179,9 +1190,12 @@ ENTRY(nmi)
 	 * we don't want to enable interrupts, because then we'll end
 	 * up in an awkward situation in which IRQs are on but NMIs
 	 * are off.
+	 *
+	 * We also must not push anything to the stack before switching
+	 * stacks lest we corrupt the "NMI executing" variable.
 	 */
 
-	SWAPGS
+	SWAPGS_UNSAFE_STACK
 	cld
 	movq	%rsp, %rdx
 	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index f68e48f5f6c2..c2130aef3f9d 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -41,10 +41,18 @@
 #include <asm/timer.h>
 #include <asm/special_insns.h>
 
-/* nop stub */
-void _paravirt_nop(void)
-{
-}
+/*
+ * nop stub, which must not clobber anything *including the stack* to
+ * avoid confusing the entry prologues.
+ */
+extern void _paravirt_nop(void);
+asm (".pushsection .entry.text, \"ax\"\n"
+     ".global _paravirt_nop\n"
+     "_paravirt_nop:\n\t"
+     "ret\n\t"
+     ".size _paravirt_nop, . - _paravirt_nop\n\t"
+     ".type _paravirt_nop, @function\n\t"
+     ".popsection");
 
 /* identity function, which can be inlined */
 u32 _paravirt_ident_32(u32 x)