On Fri, Oct 02, 2026 at 11:33:10AM +0100, Peter Maydell wrote: > On Fri, 2 Oct 2026 at 11:22, Thomas Huth <[email protected]> wrote: > > > > On 01/10/2026 21.47, Peter Maydell wrote: > > > The OHCI USB controller requires software to set up an Endpoint > > > Descriptor data structure. This specifies (among other things) both > > > an EndpointNumber telling the controller which USB endpoint to talk > > > to, and a Format (F) bit which is 1 for Isochronous transfers and 0 > > > for General transfers. > > > > > > The specification requires that software matches the F bit with the > > > endpoint it's setting up the descriptor for, so that Control, Bulk > > > and Interrupt endpoints use F=0, and Isochronous endpoints use F=1. > > > It doesn't require the controller to check whether software gets this > > > right. > > > > > > The spec isn't totally clear about what happens if software creates > > > an ED with a mismatch, but I believe that the controller just trusts > > > the F bit, and tries to talk to the endpoint with the wrong sequence > > > of USB tokens (notably, isochronous transactions have no handshaking > > > and the others do). This probably results in the transfer failing. > > > > > > In hcd-ehci.c we check for the "iso transfer to non-iso endpoint" and > > > make it fail, but we don't do this in hcd-ohci.c. The result is that > > > a guest that deliberately sets up this situation can cause us to hit > > > the assertion added in commit 7b1eba96aeca, where the endpoint is not > > > isochronous and returns USB_RET_ASYNC to an iso TD handling function > > > that isn't prepared to deal with that. > > > > > > Add checks for both "iso transfer to non-iso endpoint" and "non-iso > > > transfer to iso endpoint" and make those TDs fail rather than blindly > > > sending them to the endpoint. > > > > > > Cc: [email protected] > > > Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3729
Change that to 'Related', since the assert fix you mention below is what actually Resolves that issue initially > > Looks like this issue got assigned with a CVE number, so please add: > > > > CVE: CVE-2026-7180 > > I guess we might as well, but honestly I don't think this is CVE worthy, > and I can't find any record of what that CVE number is supposed to cover > from a websearch. This issue originated on the qemu-security list, and we declared it a CVE because it was a guest triggerable use-after-free originally. > This is in OHCI, which I thought was agreed to be outside > the security envelope, and in any case it's only an assertion failure. > > The use-after-free that was the original subject of the bug report > has already been fixed by 7b1eba96aeca (which downgraded it to > "fails assertion"). Ok, that commit is the one that should have been tagged with the CVE. This commit is just a nice followup. > > thanks > -- PMM > With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|
