Re: [PATCH] bcachefs: fix build on sh4

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

On Fri, Aug 08, 2025 at 11:19:44PM -0400, Kent Overstreet wrote:
> put_user() with a 64 bit value causes an ICE on sh4.
> 
> Reported-by: Alexander Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> ---
>  fs/bcachefs/sb-counters.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/bcachefs/sb-counters.c b/fs/bcachefs/sb-counters.c
> index 2b4b8445d418..9fa2c568c985 100644
> --- a/fs/bcachefs/sb-counters.c
> +++ b/fs/bcachefs/sb-counters.c
> @@ -136,7 +136,7 @@ long bch2_ioctl_query_counters(struct bch_fs *c,
>  				? percpu_u64_get(&c->counters[i])
>  				: c->counters_on_mount[i];
>  
> -			ret = put_user(v, &user_arg->d[stable]);
> +			ret = copy_to_user_errcode(&user_arg->d[stable], &v, sizeof(v));
>  			if (ret)
>  				return ret;
>  		}

If anything, that's the wrong place - put_user() on 64bit *is* allowed, whatever
the architecture.  See __put_user_u64() in arch/sh/include/asm/uaccess_32.h;
it is supposed to work (and it certainly isn't supposed to trigger an ICE,
so ultimately it's a gcc bug).