Re: [PATCH] erofs: fix kvcalloc() misuse with __GFP_NOFAIL

[Gao Xiang]

Hi Chao,

On 2023/1/9 18:34, Chao Yu wrote:
> On 2023/1/6 13:06, Gao Xiang wrote:
> > On 2023/1/6 11:19, Gao Xiang wrote:
> > > As reported by syzbot [1], kvcalloc() cannot work with  __GFP_NOFAIL.
> > > Let's use kcalloc() instead.
> > >
> > > [1] https://lore.kernel.org/r/0000000000007796bd05f1852ec2@xxxxxxxxxx
> > > Reported-by: syzbot+c3729cda01706a04fb98@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > Fixes: fe3e5914e6dc ("erofs: try to leave (de)compressed_pages on stack if possible")
> > Fixes: 4f05687fd703 ("erofs: introduce struct z_erofs_decompress_backend")
> >
> > > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
> > > ---
> > >   fs/erofs/zdata.c | 8 ++++----
> > >   1 file changed, 4 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> > > index ccf7c55d477f..08e982c77985 100644
> > > --- a/fs/erofs/zdata.c
> > > +++ b/fs/erofs/zdata.c
> > > @@ -1032,12 +1032,12 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
> > >       if (!be->decompressed_pages)
> > >           be->decompressed_pages =
> > > -            kvcalloc(be->nr_pages, sizeof(struct page *),
> > > -                 GFP_KERNEL | __GFP_NOFAIL);
> > > +            kcalloc(be->nr_pages, sizeof(struct page *),
> > > +                GFP_KERNEL | __GFP_NOFAIL);
> > >       if (!be->compressed_pages)
> > >           be->compressed_pages =
> > > -            kvcalloc(pclusterpages, sizeof(struct page *),
> > > -                 GFP_KERNEL | __GFP_NOFAIL);
> > > +            kcalloc(pclusterpages, sizeof(struct page *),
> > > +                GFP_KERNEL | __GFP_NOFAIL);
>
> How about using kfree instead of kvfree for .decompressed_pages and
> .compressed_pages memory release? It's trivial though.

Yeah, thanks for catching! I will send v2 to fix these.

Thanks,
Gao Xiang

> Anyway, feel free to add:
>
> Reviewed-by: Chao Yu <chao@xxxxxxxxxx>
>
> Thanks,
>
> > >       z_erofs_parse_out_bvecs(be);
> > >       err2 = z_erofs_parse_in_bvecs(be, &overlapped);