linux-kernel - Re: [PATCH] xfs: Fix uninitialized variable in xfs_reflink_reserve_cow

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Message-ID: <20161017120843.GA9906@infradead.org>
Date:   Mon, 17 Oct 2016 05:08:43 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Dave Chinner <david@...morbit.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: Fix uninitialized variable in
 xfs_reflink_reserve_cow_range()

On Mon, Oct 17, 2016 at 12:16:44PM +0200, Geert Uytterhoeven wrote:
> with gcc 4.1.2:
> 
>     fs/xfs/xfs_reflink.c: In function ‘xfs_reflink_reserve_cow_range’:
>     fs/xfs/xfs_reflink.c:327: warning: ‘error’ may be used uninitialized in this function
> 
> Indeed, if "count" is zero, the function will return an uninitialized
> error value.
> 
> While "count" is unlikely to be zero, this function is called through
> the public iomap API. Hence fix this by preinitializing error to zero.

The iomap API should never call in with a zero count, but I think the
initialization is a fine safety net anyway:

Reviewed-by: Christoph Hellwig <hch@....de>

Btw, what compiler did you get this from?  I haven't seen it, but then
again I recently missed a lot of initializers without compiler warnings,
so either something changed in the Debian stable gcc or our build
system recently..