[hackers] Re: [sbase][PATCH] dd: fix for ibs * count < obs

From: phoebos <ben_AT_bvnf.space>
Date: Thu, 22 Dec 2022 01:00:39 +0000

I thought this message had gone through but it doesn't appear in the
mailing list archive. I added some context to my patch below, and would
appreciate any feedback or confirmation that the email got through?

Thanks

On Tue, Nov 29, 2022 at 22:27:59 +0000, phoebos wrote:
> Perhaps I should add some context.
>
> Running:
>
> yes | dd ibs=1 count=1
>
> reports that 512 bytes are read:
>
> 512+0 records in
> 1+0 records out
>
> Only one byte should be read, as occurs with GNU and busybox dd:
>
> 1+0 records in
> 0+1 records out
>
> I believe the reason for this bug in sbase is because of the comparison
> with obs in the below loop, which overlooks cases such as these.
>
> All feedback is welcome. Is this an appropriate fix to the bug?
>
> phoebos
>
> On Tue, Nov 22, 2022 at 16:28:35 +0000, phoebos wrote:
> > Previously, running `dd ibs=1 count=1` read 512 bytes rather than 1.
> > ---
> > dd.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/dd.c b/dd.c
> > index 6061048..4081eca 100644
> > --- a/dd.c
> > +++ b/dd.c
> > _AT_@ -174,7 +174,7 @@ main(int argc, char *argv[])
> > /* XXX: handle non-seekable files */
> > }
> > while (!eof && (count == -1 || ifull + ipart < count)) {
> > - while (ipos - opos < obs) {
> > + while (ipos - opos < obs && ifull + ipart < count) {
> > ret = read(ifd, buf + ipos, ibs);
> > if (ret == 0) {
> > eof = 1;
> > --
> > 2.38.1
> >
Received on Thu Dec 22 2022 - 02:00:39 CET