Re: [PATCH] ceph: fix type promotion bug on 32bit systems

[Luis Henriques <lhenriques@suse.de>]

Dan Carpenter <dan.carpenter@linaro.org> writes:

> In this code "ret" is type long and "src_objlen" is unsigned int.  The
> problem is that on 32bit systems, when we do the comparison signed longs
> are type promoted to unsigned int.  So negative error codes from
> do_splice_direct() are treated as success instead of failure.
>
> Fixes: 1b0c3b9f91f0 ("ceph: re-org copy_file_range and fix some error paths")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> ---
> 32bit is so weird and ancient.  It's strange to think that unsigned int
> has more positive bits than signed long.

Yikes! Thanks for catching this, Dan.  Really tricky.  I guess you used
some static analysis tool (smatch?) to highlight this issue for you,
right?

Anyway, feel free to add my

Reviewed-by: Luis Henriques <lhenriques@suse.de>

Cheers,
-- 
Luís


>
> fs/ceph/file.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index b1da02f5dbe3..b5f8038065d7 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -2969,7 +2969,7 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
>  		ret = do_splice_direct(src_file, &src_off, dst_file,
>  				       &dst_off, src_objlen, flags);
>  		/* Abort on short copies or on error */
> -		if (ret < src_objlen) {
> +		if (ret < (long)src_objlen) {
>  			dout("Failed partial copy (%zd)\n", ret);
>  			goto out;
>  		}
> -- 
>
> 2.39.2
>