Messages in this thread | | | Date | Thu, 25 Aug 2022 14:10:52 +0200 | Subject | Re: [PATCH v3] xen/privcmd: fix error exit of privcmd_ioctl_dm_op() | From | Juergen Gross <> |
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On 25.08.22 13:58, Jan Beulich wrote: > On 25.08.2022 13:40, Juergen Gross wrote: >> --- a/drivers/xen/privcmd.c >> +++ b/drivers/xen/privcmd.c >> @@ -581,7 +581,7 @@ static int lock_pages( >> struct privcmd_dm_op_buf kbufs[], unsigned int num, >> struct page *pages[], unsigned int nr_pages, unsigned int *pinned) >> { >> - unsigned int i; >> + unsigned int i, off = 0; >> >> for (i = 0; i < num; i++) { >> unsigned int requested; >> @@ -589,19 +589,23 @@ static int lock_pages( >> >> requested = DIV_ROUND_UP( >> offset_in_page(kbufs[i].uptr) + kbufs[i].size, >> - PAGE_SIZE); >> + PAGE_SIZE) - off; >> if (requested > nr_pages) >> return -ENOSPC; >> >> page_count = pin_user_pages_fast( >> - (unsigned long) kbufs[i].uptr, >> + (unsigned long)kbufs[i].uptr + off * PAGE_SIZE, >> requested, FOLL_WRITE, pages); >> - if (page_count < 0) >> - return page_count; >> + if (page_count <= 0) >> + return page_count ? : -EFAULT; >> >> *pinned += page_count; >> nr_pages -= page_count; >> pages += page_count; >> + >> + off = requested - page_count; >> + if (off) >> + i--; >> } > > Initially I thought this would go wrong only on the 3rd iteration, but > meanwhile I think it's wrong already on the 2nd. What I think you need > is > > if (page_count < requested) > i--; > off += page_count; > > or with the i++ from the loop header absorbed here > > if (page_count == requested) > i++; > off += page_count; > > Plus of course off needs resetting to zero whenever i advances. I.e. > > if (page_count == requested) { > i++; > off = 0; > } else { > off += page_count; > }
Yeah, or:
off = (page_count == requested) ? 0 : off + page_count; i += !off;
Juergen [unhandled content-type:application/pgp-keys][unhandled content-type:application/pgp-signature] | |