[PATCH] Fix /proc/pid/pagemap end address calculation

[PATCH] Fix /proc/pid/pagemap end address calculation

[Dave Boutcher]

When dumping vma information the pagemap_read routine calculates
the minimum of what the user asks for and the end of the vma.
Unfortunately the code uses vma->vm_start rather than vma->vm_end
which can result in the end address being before the start, and
a nasty never-ending loop in the kernel.

Diffed against 2.6.23-rc1-mm2

Signed-off-by: Dave Boutcher <boutcher@cs.umn.edu>
---
 fs/proc/task_mmu.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index b2baeab..b12740c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -671,7 +671,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 			ret = -EIO;
 			goto out_mm;
 		}
-		vend = min(vma->vm_start - 1, end - 1) + 1;
+		vend = min(vma->vm_end - 1, end - 1) + 1;
 		ret = pagemap_fill(&pm, vend);
 		if (ret || !pm.count)
 			break;
-- 
1.4.4.2

Re: [PATCH] Fix /proc/pid/pagemap end address calculation

[Matt Mackall]

On Sun, Aug 05, 2007 at 09:03:28PM -0500, Dave Boutcher wrote:
> 
> When dumping vma information the pagemap_read routine calculates
> the minimum of what the user asks for and the end of the vma.
> Unfortunately the code uses vma->vm_start rather than vma->vm_end
> which can result in the end address being before the start, and
> a nasty never-ending loop in the kernel.
> 
> Diffed against 2.6.23-rc1-mm2
> 
> Signed-off-by: Dave Boutcher <boutcher@cs.umn.edu>

Thanks, Dave. I've added this fix to my local tree. It's still in a
broken state at the moment, so Andrew, feel free to pick this up.

Acked-by: Matt Mackall <mpm@selenic.com>

> ---
>  fs/proc/task_mmu.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index b2baeab..b12740c 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -671,7 +671,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
>  			ret = -EIO;
>  			goto out_mm;
>  		}
> -		vend = min(vma->vm_start - 1, end - 1) + 1;
> +		vend = min(vma->vm_end - 1, end - 1) + 1;
>  		ret = pagemap_fill(&pm, vend);
>  		if (ret || !pm.count)
>  			break;
> -- 
> 1.4.4.2
> 
> -
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-- 
Mathematics is the supreme nostalgia of our time.