[PATCH v2] erofs-utils: lib: fix infinite loop on EOF in erofs_io_xcopy

[Ajay Rajera]

yeah, I checked it and you are right.
I have sent patch v3 to fix this.
Thanks,
Ajay Rajera.

On Sun, 22 Mar 2026 at 08:53, Gao Xiang <hsiangkao at linux.alibaba.com> wrote:
>
>
>
> On 2026/3/21 11:42, Ajay Rajera wrote:
> > Thank you, I appreciate it.
> >
> > best regards,
> > Ajay Rajera
> >
> > On Sat, 21 Mar 2026 at 08:41, Gao Xiang <hsiangkao at linux.alibaba.com> wrote:
> >>
> >>
> >>
> >> On 2026/3/21 02:50, Ajay Rajera wrote:
> >>> erofs_io_xcopy() has a fallback do-while loop for when the
> >>> kernel fast-paths (copy_file_range/sendfile) do not handle all
> >>> the data.  The loop does:
> >>>
> >>>       ret = erofs_io_read(vin, buf, ret);
> >>>       if (ret < 0)
> >>>           return ret;
> >>>       if (ret > 0) { ... pos += ret; }
> >>>       len -= ret;
> >>>     } while (len);
> >>>
> >>> When erofs_io_read() returns 0 (EOF -- source exhausted before
> >>> all bytes were copied), only the ret < 0 and ret > 0 branches
> >>> were handled.  Since ret == 0, `len -= ret` is a no-op and
> >>> `while (len)` stays true, causing the loop to spin forever at
> >>> 100% CPU with no error and no progress.
> >>>
> >>> This can be triggered when building an EROFS image from an input
> >>> file that is shorter than expected -- e.g. a truncated source
> >>> file, a pipe/FIFO that closes early, or a file being modified
> >>> concurrently during mkfs.
> >>>
> >>> Fix it by treating a zero return as an error (-EIO) so the
> >>> caller fails cleanly instead of hanging indefinitely.
> >>>
> >>> Also fix the long-standing 'pading' -> 'padding' typo in the
> >>> short-read diagnostic message of erofs_dev_read().
> >>>
> >>> Signed-off-by: Ajay Rajera <newajay.11r at gmail.com>
> >>
> >> Look good to me, will apply.
>
> This patch cause a regression which can cause build failure:
> https://github.com/erofs/erofsnightly/actions/runs/23392598146/job/68049898517
>
> It can be reproduced by:
> $ mkfs/mkfs.erofs --zfeature-bits=78 foo.erofs linux-5.4.140
>
> I dropped this patch.
>
> Thanks,
> Gao Xiang
>
> >>
> >> Thanks,
> >> Gao Xiang
>