Re: [PATCH] isofs: fix timestamps beyond 2027

[Al Viro <viro@ZenIV.linux.org.uk>]

On Thu, Oct 19, 2017 at 11:50:18AM +0200, Arnd Bergmann wrote:
> isofs uses a 'char' variable to load the number of years since
> 1900 for an inode timestamp. On architectures that use a signed
> char type by default, this results in an invalid date for
> anything beyond 2027.
> 
> This adds a cast to 'u8' for the year number, which should extend
> the shelf life of the file system until 2155.
> 
> This should be backported to all kernels that might still be
> in use by that date.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  fs/isofs/util.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/isofs/util.c b/fs/isofs/util.c
> index 005a15cfd30a..f40796c4c6c2 100644
> --- a/fs/isofs/util.c
> +++ b/fs/isofs/util.c
> @@ -20,7 +20,7 @@ int iso_date(char * p, int flag)
>  	int year, month, day, hour, minute, second, tz;
>  	int crtime;
>  
> -	year = p[0];
> +	year = (int)(u8)p[0];

This is BS; just turn that
        char time[7];
in struct stamp into
	unsigned char time[7];
and adjust iso_date() accordingly.  Or make that
sucker actually take struct stamp *, while we are at it.

And I'd suggest going through the rest of on-disk structures in
rock.h and looking for other trouble of that sort.