[PATCH v3] xen/arm: Fix the issue in cmp_mmio_handler used in find_mmio_handler

[PATCH v3] xen/arm: Fix the issue in cmp_mmio_handler used in find_mmio_handler

[Bhupinder Thakur]

This patch fixes the wrong range check done in cmp_mmio_handler().

This function returns -1 , 0 or 1  based on whether the key value
is below the range, in the range or above the range where the range is
(start, start+size). However, it should check against (start, start+size-1)
because start+size falls outside the range.

This resulted in returning a wrong mmio_handler for a given mmio address which
happened to be start+size.

This bug was introduced when the mmio region search switched from
linear search to binary search in the following commit:

8047e09 "xen/arm: io: Use binary search for mmio handler lookup".

Signed-off-by: Bhupinder Thakur <bhupinder.thakur@linaro.org>
---
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien.grall@arm.com>

This patch may have to be back ported to 4.8 also.

 xen/arch/arm/io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index e216128..c748d8f 100644
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -79,7 +79,7 @@ static int cmp_mmio_handler(const void *key, const void *elem)
     if ( handler0->addr < handler1->addr )
         return -1;
 
-    if ( handler0->addr > (handler1->addr + handler1->size) )
+    if ( handler0->addr >= (handler1->addr + handler1->size) )
         return 1;
 
     return 0;
-- 
2.7.4


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Re: [PATCH v3] xen/arm: Fix the issue in cmp_mmio_handler used in find_mmio_handler

[Stefano Stabellini]

On Fri, 29 Sep 2017, Bhupinder Thakur wrote:
> This patch fixes the wrong range check done in cmp_mmio_handler().
> 
> This function returns -1 , 0 or 1  based on whether the key value
> is below the range, in the range or above the range where the range is
> (start, start+size). However, it should check against (start, start+size-1)
> because start+size falls outside the range.
> 
> This resulted in returning a wrong mmio_handler for a given mmio address which
> happened to be start+size.
> 
> This bug was introduced when the mmio region search switched from
> linear search to binary search in the following commit:
> 
> 8047e09 "xen/arm: io: Use binary search for mmio handler lookup".
> 
> Signed-off-by: Bhupinder Thakur <bhupinder.thakur@linaro.org>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

and committed

> ---
> CC: Stefano Stabellini <sstabellini@kernel.org>
> CC: Julien Grall <julien.grall@arm.com>
> 
> This patch may have to be back ported to 4.8 also.
> 
>  xen/arch/arm/io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
> index e216128..c748d8f 100644
> --- a/xen/arch/arm/io.c
> +++ b/xen/arch/arm/io.c
> @@ -79,7 +79,7 @@ static int cmp_mmio_handler(const void *key, const void *elem)
>      if ( handler0->addr < handler1->addr )
>          return -1;
>  
> -    if ( handler0->addr > (handler1->addr + handler1->size) )
> +    if ( handler0->addr >= (handler1->addr + handler1->size) )
>          return 1;
>  
>      return 0;
> -- 
> 2.7.4
> 

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