genirq: Prevent access beyond allocated_irqs bitmap

Lars-Peter Clausen pointed out:

   I stumbled upon this while looking through the existing archs using
   SPARSE_IRQ.  Even with SPARSE_IRQ the NR_IRQS is still the upper
   limit for the number of IRQs.

   Both PXA and MMP set NR_IRQS to IRQ_BOARD_START, with
   IRQ_BOARD_START being the number of IRQs used by the core.

   In various machine files the nr_irqs field of the ARM machine
   defintion struct is then set to "IRQ_BOARD_START + NR_BOARD_IRQS".

   As a result "nr_irqs" will greater then NR_IRQS which then again
   causes the "allocated_irqs" bitmap in the core irq code to be
   accessed beyond its size overwriting unrelated data.

The core code really misses a sanity check there.

This went unnoticed so far as by chance the compiler/linker places
data behind that bitmap which gets initialized later on those affected
platforms.

So the obvious fix would be to add a sanity check in early_irq_init()
and break all affected platforms. Though that check wants to be
backported to stable as well, which will require to fix all known
problematic platforms and probably some more yet not known ones as
well. Lots of churn.

A way simpler solution is to allocate a slightly larger bitmap and
avoid the whole churn w/o breaking anything. Add a few warnings when
an arch returns utter crap.

Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org # .37
Cc: Haojian Zhuang <haojian.zhuang@marvell.com>
Cc: Eric Miao <eric.y.miao@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>

diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 4571ae7e085ac95ad6affb1f31d802f32064665e..99c3bc8a6fb464f1e19a00dc6e1959cb9e777b5e 100644 (file)
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -3,6 +3,12 @@
  */
 #include <linux/irqdesc.h>
 
+#ifdef CONFIG_SPARSE_IRQ
+# define IRQ_BITMAP_BITS       (NR_IRQS + 8196)
+#else
+# define IRQ_BITMAP_BITS       NR_IRQS
+#endif
+
 extern int noirqdebug;
 
 #define irq_data_to_desc(data) container_of(data, struct irq_desc, irq_data)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 282f20230e67c9c13b12ef6f30f4fb363cc84acf..2039bea31bdf4932eb2b08f91e6eb44113b7240c 100644 (file)
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -94,7 +94,7 @@ int nr_irqs = NR_IRQS;
 EXPORT_SYMBOL_GPL(nr_irqs);
 
 static DEFINE_MUTEX(sparse_irq_lock);
-static DECLARE_BITMAP(allocated_irqs, NR_IRQS);
+static DECLARE_BITMAP(allocated_irqs, IRQ_BITMAP_BITS);
 
 #ifdef CONFIG_SPARSE_IRQ
 
@@ -217,6 +217,15 @@ int __init early_irq_init(void)
        initcnt = arch_probe_nr_irqs();
        printk(KERN_INFO "NR_IRQS:%d nr_irqs:%d %d\n", NR_IRQS, nr_irqs, initcnt);
 
+       if (WARN_ON(nr_irqs > IRQ_BITMAP_BITS))
+               nr_irqs = IRQ_BITMAP_BITS;
+
+       if (WARN_ON(initcnt > IRQ_BITMAP_BITS))
+               initcnt = IRQ_BITMAP_BITS;
+
+       if (initcnt > nr_irqs)
+               nr_irqs = initcnt;
+
        for (i = 0; i < initcnt; i++) {
                desc = alloc_desc(i, node);
                set_bit(i, allocated_irqs);

diff --git a/kernel/irq/resend.c b/kernel/irq/resend.c
index 891115a929aa1dfe223b01c5f50efbc0ec35a2f7..dc49358b73fa4cdaa746e25d669389dd873ac2f2 100644 (file)
--- a/kernel/irq/resend.c
+++ b/kernel/irq/resend.c
@@ -23,7 +23,7 @@
 #ifdef CONFIG_HARDIRQS_SW_RESEND
 
 /* Bitmap to handle software resend of interrupts: */
-static DECLARE_BITMAP(irqs_resend, NR_IRQS);
+static DECLARE_BITMAP(irqs_resend, IRQ_BITMAP_BITS);
 
 /*
  * Run software resends of IRQ's