On Sat, Jun 14, 2025 at 3:54 AM Brian Foster <bfoster@xxxxxxxxxx> wrote:
>
> On Fri, Jun 13, 2025 at 05:01:14PM -0700, Joanne Koong wrote:
> > This fixes a bug in commit 63c69ad3d18a ("fuse: refactor
> > fuse_fill_write_pages()") where max_pages << PAGE_SHIFT is mistakenly
> > used as the calculation for the max_pages upper limit but there's the
> > possibility that copy_folio_from_iter_atomic() may copy over bytes
> > from the iov_iter that are less than the full length of the folio,
> > which would lead to exceeding max_pages.
> >
> > This commit fixes it by adding a 'ap->num_folios < max_folios' check.
> >
> > Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
> > Fixes: 63c69ad3d18a ("fuse: refactor fuse_fill_write_pages()")
> > Reported-by: Brian Foster <bfoster@xxxxxxxxxx>
> > Closes: https://lore.kernel.org/linux-fsdevel/aEq4haEQScwHIWK6@bfoster/
> > ---
>
> This resolves the problem for me as well. Thanks again..
>
> Tested-by: Brian Foster <bfoster@xxxxxxxxxx>
>
> > fs/fuse/file.c | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> > index 3d0b33be3824..a05a589dc701 100644
> > --- a/fs/fuse/file.c
> > +++ b/fs/fuse/file.c
> > @@ -1147,7 +1147,7 @@ static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,
> > static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
> > struct address_space *mapping,
> > struct iov_iter *ii, loff_t pos,
> > - unsigned int max_pages)
> > + unsigned int max_folios)
> > {
> > struct fuse_args_pages *ap = &ia->ap;
> > struct fuse_conn *fc = get_fuse_conn(mapping->host);
> > @@ -1157,12 +1157,11 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
> > int err = 0;
> >
> > num = min(iov_iter_count(ii), fc->max_write);
> > - num = min(num, max_pages << PAGE_SHIFT);
> >
> > ap->args.in_pages = true;
> > ap->descs[0].offset = offset;
> >
> > - while (num) {
> > + while (num && ap->num_folios < max_folios) {
> > size_t tmp;
> > struct folio *folio;
> > pgoff_t index = pos >> PAGE_SHIFT;
> > --
> > 2.47.1
> >
>
Miklos or Christian, could this fix be added to the next release candidate?
Thanks,
Joanne
