linux-kernel - Re: [PATCH 1/2] iov_iter: iterate_folioq: fix handling of offset >= folio size

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <650269.1754991257@warthog.procyon.org.uk>
Date: Tue, 12 Aug 2025 10:34:17 +0100
From: David Howells <dhowells@...hat.com>
To: asmadeus@...ewreck.org
Cc: dhowells@...hat.com, "Matthew Wilcox (Oracle)" <willy@...radead.org>,
    Christian Brauner <brauner@...nel.org>,
    Alexander Viro <viro@...iv.linux.org.uk>,
    Andrew Morton <akpm@...ux-foundation.org>,
    Maximilian Bosch <maximilian@...sch.me>, Ryan Lahfa <ryan@...fa.xyz>,
    Christian Theune <ct@...ingcircus.io>,
    Arnout Engelen <arnout@...t.net>, linux-kernel@...r.kernel.org,
    linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
    stable@...r.kernel.org
Subject: Re: [PATCH 1/2] iov_iter: iterate_folioq: fix handling of offset >= folio size

asmadeus@...ewreck.org wrote:

> There should be a `if (slot == folioq_nr_slots(folioq)) break` check
> somewhere as well? Or is the iov_iter guaranteed to always 1/ have some
> data and 2/ either be big enough or have remaining data in a step?

We should handle both cases.  I think the other iteration functions
will. iov_iter_extractg_folioq_pages(), for example, wraps it in a
conditional:

		if (offset < fsize) {
			part = umin(part, umin(maxsize - extracted, fsize - offset));
			i->count -= part;
			i->iov_offset += part;
			extracted += part;

			p[nr++] = folio_page(folio, offset / PAGE_SIZE);
		}

David