linux-kernel - Re: [PATCH]: xarray: Fix potential out of bounds access

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Date:   Mon, 14 Jan 2019 22:14:18 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH]: xarray: Fix potential out of bounds access

On Mon, Jan 14, 2019 at 11:01:20AM -0800, Matthew Wilcox wrote:
> On Mon, Jan 14, 2019 at 09:47:41PM +0300, Cyrill Gorcunov wrote:
> > Since the mark is used as an array index we should use
> > preincrement to not access the XA_MARK_MAX index.
> 
> But XA_MARK_MAX is inclusive:
> 
> include/linux/xarray.h:#define XA_MARK_MAX              XA_MARK_2

Indeed, I misread the variable name.

> so we actually want to access XA_MARK_MAX.  Now, we don't have a test
> in the test-suite that fails as a result of your patch, so that needs to get
> fixed.  How about this:

Looks great. Thank you!