2021-09-10 03:28:23

by Jiasheng Jiang

Subject: [PATCH 6/6] irq: Potentially 'offset out of size' bug

The find_next_bit() use nr_irqs as size, and using it without
any check might cause its returned value out of the size

Signed-off-by: Jiang Jiasheng <[email protected]>
---
kernel/irq/irqdesc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 4a617d73..5bb310a 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -820,7 +820,8 @@ EXPORT_SYMBOL_GPL(__irq_alloc_descs);
*/
unsigned int irq_get_next_irq(unsigned int offset)
{
- return find_next_bit(allocated_irqs, nr_irqs, offset);
+ offset = find_next_bit(allocated_irqs, nr_irqs, offset);
+ return offset < nr_irqs ? offset : nr_irqs;
}

struct irq_desc *
--
2.7.4

2021-09-10 10:29:10

by Thomas Gleixner

Subject: Re: [PATCH 6/6] irq: Potentially 'offset out of size' bug

On Fri, Sep 10 2021 at 03:26, Jiang Jiasheng wrote:
> The find_next_bit() use nr_irqs as size, and using it without
> any check might cause its returned value out of the size

Why exactly is this a problem? The return value has to be checked at the
call site anyway.

Thanks,

tglx