On Fri, May 23, 2025 at 8:59 AM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> Hello Joanne Koong,
>
> This is a semi-automatic email about new static checker warnings.
>
> Commit f008a4390bde ("fuse: support copying large folios") from May
> 12, 2025, leads to the following Smatch complaint:
>
> fs/fuse/dev.c:1103 fuse_copy_folio()
> warn: variable dereferenced before check 'folio' (see line 1101)
>
> fs/fuse/dev.c
> 1100 struct folio *folio = *foliop;
> 1101 size_t size = folio_size(folio);
> ^^^^^
> The patch adds an unchecked dereference
>
> 1102
> 1103 if (folio && zeroing && count < size)
> ^^^^^
> and it also adds this check for NULL which is too late.
>
> 1104 folio_zero_range(folio, 0, size);
> 1105
Thanks for flagging. I looked through where we call fuse_copy_folio()
and we'll never run into the case where folio is null, so all the "if
folio" branches inside there can probably be cleaned up with a WARN_ON
check.
I'll submit a patch that fixes this commit and a separate patch that
cleans up the if folio check.
>
> regards,
> dan carpenter
