linux-kernel - Re: [PATCH v2 1/1] lib/ioremap.c: avoid endless loop under ioremapping page unaligned ranges

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Date:   Fri, 23 Sep 2016 13:53:03 +0800
From:   zijun_hu <zijun_hu@...o.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, zijun_hu@....com,
        tj@...nel.org, mingo@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, mgorman@...hsingularity.net
Subject: Re: [PATCH v2 1/1] lib/ioremap.c: avoid endless loop under
 ioremapping page unaligned ranges

On 09/21/2016 12:19 PM, zijun_hu wrote:
> From: zijun_hu <zijun_hu@....com>
> 
> endless loop maybe happen if either of parameter addr and end is not
> page aligned for kernel API function ioremap_page_range()
> 
> in order to fix this issue and alert improper range parameters to user
> WARN_ON() checkup and rounding down range lower boundary are performed
> firstly, loop end condition within ioremap_pte_range() is optimized due
> to lack of relevant macro pte_addr_end()
> 
> Signed-off-by: zijun_hu <zijun_hu@....com>
> ---
>  lib/ioremap.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/ioremap.c b/lib/ioremap.c
> index 86c8911..911bdca 100644
> --- a/lib/ioremap.c
> +++ b/lib/ioremap.c
> @@ -64,7 +64,7 @@ static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,
>  		BUG_ON(!pte_none(*pte));
>  		set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot));
>  		pfn++;
> -	} while (pte++, addr += PAGE_SIZE, addr != end);
> +	} while (pte++, addr += PAGE_SIZE, addr < end && addr >= PAGE_SIZE);
>  	return 0;
>  }
>  
> @@ -129,7 +129,9 @@ int ioremap_page_range(unsigned long addr,
>  	int err;
>  
>  	BUG_ON(addr >= end);
> +	WARN_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
>  
> +	addr = round_down(addr, PAGE_SIZE);
>  	start = addr;
>  	phys_addr -= addr;
>  	pgd = pgd_offset_k(addr);
>
From: zijun_hu <zijun_hu@....com>

s/WARN_ON()/WARN_ON_ONCE()/ to reduce warning messages

Signed-off-by: zijun_hu <zijun_hu@....com>
---
 lib/ioremap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/ioremap.c b/lib/ioremap.c
index 911bdca..974e88b 100644
--- a/lib/ioremap.c
+++ b/lib/ioremap.c
@@ -129,7 +129,7 @@ int ioremap_page_range(unsigned long addr,
 	int err;
 
 	BUG_ON(addr >= end);
-	WARN_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
+	WARN_ON_ONCE(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
 
 	addr = round_down(addr, PAGE_SIZE);
 	start = addr;
-- 
1.9.1