On Mon, Aug 28, 2023 at 6:11 PM Philippe Mathieu-Daudé
<phi...@linaro.org> wrote:
>
> On 27/8/23 13:07, Mauro Matteo Cascella wrote:
> > On Sat, Aug 26, 2023 at 4:31 PM Mauro Matteo Cascella
> > <mcasc...@redhat.com> wrote:
> >>
> >> On Fri, Jun 24, 2022 at 4:40 PM Mauro Matteo Cascella
> >> <mcasc...@redhat.com> wrote:
> >>>
> >>> rocker_tlv_parse_nested could return early because of no group ids in
> >>> the group_tlvs. In such case tlvs is NULL; tlvs[i + 1] in the next
> >>> for-loop will deref the NULL pointer.
> >
> > Looking at the code once again, tlvs is a pointer to a g_new0
> > allocated memory, so I don't know how it can be NULL after
> > rocker_tlv_parse_nested (unless g_new0 returns NULL in the first
> > place). I do not recall the details of this bug. Arayz?
>
> Per <glib.h>:
>
>    If any call to allocate memory using functions g_new(), g_new0(),
>    g_renew(), g_malloc(), g_malloc0(), g_malloc0_n(), g_realloc(), and
>    g_realloc_n() fails, the application is terminated. This also means
>    that there is no need to check if the call succeeded. On the other
>    hand, g_try_...() family of functions returns NULL on failure that
>    can be used as a check for unsuccessful memory allocation. The
>    application is not terminated in this case.
>
>
> group->l2_flood.group_count is a uint16_t, so up to UINT16_MAX = 0xffff.
>
> So:
>
>    tlvs = g_new0(RockerTlv *, group->l2_flood.group_count + 1);
>
> is at most an malloc(0x10000 * sizeof(void *)) = 0x80000 = 512 KiB.
>
> QEMU use way bigger heap allocations.
>
> I don't know the net/ subsystem enough to have an idea about how many
> concurrent packets can be processed by this device model, but I'd be
> surprised if this triggers a OOM.
>
> As usual, do you have a reproducer?

I just found the original bug report and opened a new issue upstream.
See https://gitlab.com/qemu-project/qemu/-/issues/1851.

> >> Someone somehow reserved a new CVE for this bug, published a few days
> >> ago here: https://nvd.nist.gov/vuln/detail/CVE-2022-36648.
> >>
> >> Not only is this not CVE worthy (rocker code does not fall under the
> >> KVM virtualization use case [1]) but what's most concerning is that it
> >> got a CVSS score of 10 :/
> >>
> >> I'm going to dispute this CVE. Hopefully, it will be rejected soon. In
> >> any case, can we get this patch merged?
> >>
> >> [1] https://www.qemu.org/docs/master/system/security.html
> >>
> >> Thanks,
> >>
> >>> Signed-off-by: Mauro Matteo Cascella <mcasc...@redhat.com>
> >>> Reported-by: <aray...@icloud.com>
> >>> ---
> >>>   hw/net/rocker/rocker_of_dpa.c | 5 +++++
> >>>   1 file changed, 5 insertions(+)
> >>>
> >>> diff --git a/hw/net/rocker/rocker_of_dpa.c b/hw/net/rocker/rocker_of_dpa.c
> >>> index b3b8c5bb6d..1611b79227 100644
> >>> --- a/hw/net/rocker/rocker_of_dpa.c
> >>> +++ b/hw/net/rocker/rocker_of_dpa.c
> >>> @@ -2039,6 +2039,11 @@ static int of_dpa_cmd_add_l2_flood(OfDpa *of_dpa, 
> >>> OfDpaGroup *group,
> >>>       rocker_tlv_parse_nested(tlvs, group->l2_flood.group_count,
> >>>                               group_tlvs[ROCKER_TLV_OF_DPA_GROUP_IDS]);
> >>>
> >>> +    if (!tlvs) {
> >>> +        err = -ROCKER_EINVAL;
> >>> +        goto err_out;
> >>> +    }
> >>> +
> >>>       for (i = 0; i < group->l2_flood.group_count; i++) {
> >>>           group->l2_flood.group_ids[i] = rocker_tlv_get_le32(tlvs[i + 1]);
> >>>       }
> >>> --
> >>> 2.35.3
> >>>
> >>
> >
>

-- 
Mauro Matteo Cascella
Red Hat Product Security
PGP-Key ID: BB3410B0


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