Re: [PATCH] lib: libfile: Fix copying files to a non existing destination

[Sascha Hauer <s.hauer@pengutronix.de>]

On Fri, Jan 13, 2017 at 10:15:59AM +0100, Teresa Remmet wrote:
> If the destination file does not exist the stat call to check the file
> type fails. Extend the check of the stat return value.
> To allow to copy files to a new destination.

Uh, I am glad this is not in a release yet.

> 
> Fixes commit 0ec6bd3e1be8 ("libfile: copy_file: Only open
> regular files with O_TRUNC")
> 
> Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
> ---
>  lib/libfile.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/libfile.c b/lib/libfile.c
> index 049ec32..3742314 100644
> --- a/lib/libfile.c
> +++ b/lib/libfile.c
> @@ -276,14 +276,14 @@ int copy_file(const char *src, const char *dst, int verbose)
>  		goto out;
>  	}
>  
> -	ret = stat(dst, &dststat);
> -	if (ret)
> -		goto out;
> -
>  	mode = O_WRONLY | O_CREAT;
>  
> -	if (S_ISREG(dststat.st_mode))
> +	ret = stat(dst, &dststat);
> +	/* Set O_TRUNC only if file does not exist or is a regular file */
> +	if (ret == -ENOENT || (!ret && S_ISREG(dststat.st_mode)))
>  		mode |= O_TRUNC;
> +	else if (ret)
> +		goto out;

This is a bit hard to follow. When the destination file does not exist
then we do not need the O_TRUNC flag. How about:

	if (ret && ret != -ENOENT)
		goto out;
	if (!ret && S_ISREG(dststat.st_mode))
		mode |= O_TRUNC;

Sascha

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