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Subject[tip:irq/core] genirq: Use IRQ_BITMAP_BITS as search size in irq_alloc_descs()
Commit-ID:  ed4dea6e0e33a3e58d8b77b775a8f0e433e7a005
Gitweb: http://git.kernel.org/tip/ed4dea6e0e33a3e58d8b77b775a8f0e433e7a005
Author: Yinghai Lu <yinghai@kernel.org>
AuthorDate: Sat, 19 Feb 2011 11:07:37 -0800
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 21 Feb 2011 21:20:00 +0100

genirq: Use IRQ_BITMAP_BITS as search size in irq_alloc_descs()

The runtime expansion of nr_irqs does not take into account that
bitmap_find_next_zero_area() returns "start" + size in case the search
for an matching zero area fails. That results in a start value which
can be completely off and is not covered by the following
expand_nr_irqs() and possibly outside of the absolute limit. But we
use it without further checking.

Use IRQ_BITMAP_BITS as the limit for the bitmap search and expand
nr_irqs when the start bit is beyond nr_irqs. So start is always
pointing to the correct area in the bitmap. nr_irqs is just the limit
for irq enumerations, not the real limit for the irq space.

[ tglx: Let irq_expand_nr_irqs() take the new upper end so we do not
expand nr_irqs more than necessary. Made changelog readable ]

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <4D6014F9.8040605@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/irq/irqdesc.c | 15 ++++++++-------
1 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 394ab6a..dbccc79 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -207,11 +207,11 @@ struct irq_desc * __ref irq_to_desc_alloc_node(unsigned int irq, int node)
return NULL;
}

-static int irq_expand_nr_irqs(unsigned int cnt)
+static int irq_expand_nr_irqs(unsigned int nr)
{
- if (nr_irqs + cnt > IRQ_BITMAP_BITS)
+ if (nr > IRQ_BITMAP_BITS)
return -ENOMEM;
- nr_irqs += cnt;
+ nr_irqs = nr;
return 0;
}

@@ -298,7 +298,7 @@ static inline int alloc_descs(unsigned int start, unsigned int cnt, int node)
return start;
}

-static int irq_expand_nr_irqs(unsigned int cnt)
+static int irq_expand_nr_irqs(unsigned int nr)
{
return -ENOMEM;
}
@@ -346,13 +346,14 @@ irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node)

mutex_lock(&sparse_irq_lock);

- start = bitmap_find_next_zero_area(allocated_irqs, nr_irqs, from, cnt, 0);
+ start = bitmap_find_next_zero_area(allocated_irqs, IRQ_BITMAP_BITS,
+ from, cnt, 0);
ret = -EEXIST;
if (irq >=0 && start != irq)
goto err;

- if (start >= nr_irqs) {
- ret = irq_expand_nr_irqs(cnt);
+ if (start + cnt > nr_irqs) {
+ ret = irq_expand_nr_irqs(start + cnt);
if (ret)
goto err;
}

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