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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1785311873; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=YOZULDzniFj/gLf5QOhTIR4ke0Ws5kBaUguwO34pDsM=; b=hEbyikAMYR17Ss9aqQco3+S7NR7/rn1ZUrs2IUPh7U0W2KPSMLemjeOWUH3xg5QiYs+Tdy OZ6khj05F8V4rw3GZcPlEOO/IvT1gqpkvVyDHt7Zo0XvBSFuYXRGORUuhzJyvbz8BSUECt klQ+D9poiY/0ETfogWXAdiG5HkuBVcw= X-MC-Unique: BPl52zrpM8Kk-4MhG7L-mw-1 X-Mimecast-MFC-AGG-ID: BPl52zrpM8Kk-4MhG7L-mw_1785311870 From: marcandre.lureau@redhat.com To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Subject: [PATCH] hw/usb/dev-smartcard-reader: fix OOB read from pending bulk-in ring Date: Wed, 29 Jul 2026 11:57:43 +0400 Message-ID: <20260729075743.333920-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists1p.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=marcandre.lureau@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -36 X-Spam_score: -3.7 X-Spam_bar: --- X-Spam_report: (-3.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.58, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1785311915869158500 From: Marc-Andr=C3=A9 Lureau ccid_bulk_in_get() decrements bulk_in_pending_num when a slot becomes active, but the slot is only truly free after ccid_bulk_in_release(). A guest can fill all 8 ring slots, partially read one (leaving pos non-zero), then send another command whose response reuses the active slot. The stale pos > new len makes the uint32_t subtraction in ccid_bulk_in_copy_to_guest() wrap, reading past data[]. Move the decrement to ccid_bulk_in_release() so the slot stays busy until then. Add an assert(pos <=3D len) before the substraction. In practice, the device advertises bMaxCCIDBusySlots=3D1, so a conforming host never has more than one command in flight and the ring never fills. Fixes: CVE-2026-18204 Fixes: 367071447ec5 ("usb-ccid: add CCID bus") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4086 Reported-by: Warisjeet Singh Signed-off-by: Marc-Andr=C3=A9 Lureau --- hw/usb/dev-smartcard-reader.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/hw/usb/dev-smartcard-reader.c b/hw/usb/dev-smartcard-reader.c index 964c142d1066..5f8b95be46b2 100644 --- a/hw/usb/dev-smartcard-reader.c +++ b/hw/usb/dev-smartcard-reader.c @@ -580,6 +580,7 @@ static void ccid_bulk_in_release(USBCCIDState *s) assert(s->current_bulk_in !=3D NULL); s->current_bulk_in->pos =3D 0; s->current_bulk_in =3D NULL; + s->bulk_in_pending_num--; } =20 static void ccid_bulk_in_get(USBCCIDState *s) @@ -587,8 +588,6 @@ static void ccid_bulk_in_get(USBCCIDState *s) if (s->current_bulk_in !=3D NULL || s->bulk_in_pending_num =3D=3D 0) { return; } - assert(s->bulk_in_pending_num > 0); - s->bulk_in_pending_num--; s->current_bulk_in =3D &s->bulk_in_pending[(s->bulk_in_pending_start++) % BULK_IN_PENDING= _NUM]; } @@ -1078,6 +1077,7 @@ static void ccid_bulk_in_copy_to_guest(USBCCIDState *= s, USBPacket *p, =20 ccid_bulk_in_get(s); if (s->current_bulk_in !=3D NULL) { + assert(s->current_bulk_in->pos <=3D s->current_bulk_in->len); len =3D MIN(s->current_bulk_in->len - s->current_bulk_in->pos, p->iov.size); if (len) { --=20 2.55.0