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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784211074; 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=JN4xw6EkBwRVM1+hkts9J3dPnOr5XGjMYNzNm35Ih5Q=; b=bBAm8qN+4L2U2N1AE7/unrRK+rh2ROFyfPL89UWeiwNkGpYtHMfXuYbB5DqcQ7FvepOPxX lib0JgWfVgwTH3gHCFW6HtkX5FbxT3nh/QhunX5GoyYlosUgCZ3yFhIoIu2+DXs3no0zji wTrLdkpHkASprnn5UV3D6dcOR5Cv2NU= X-MC-Unique: LHytptUTOqGqbDhuYWCiPA-1 X-Mimecast-MFC-AGG-ID: LHytptUTOqGqbDhuYWCiPA_1784211072 From: marcandre.lureau@redhat.com To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Subject: [PATCH] usbredir: fix infinite loop and SIGFPE with zero max_packet_size Date: Thu, 16 Jul 2026 18:11:07 +0400 Message-ID: <20260716141107.3597076-1-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 10.30.177.93 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: permerror client-ip=170.10.129.124; envelope-from=marcandre.lureau@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H2=-0.01, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 autolearn=no 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: 1784211091194158500 From: Marc-Andr=C3=A9 Lureau A malicious usbredir peer can send an ep_info message resetting max_packet_size to 0 after bulk receiving has started. This causes: - infinite loop in usbredir_buffered_bulk_packet() where the splitting loop increments by max_packet_size (0) - SIGFPE in usbredir_buffered_bulk_in_complete_ftdi() from modulo by 0 - SIGFPE in usbredir_handle_buffered_bulk_in_data() from division by 0 when computing bytes_per_transfer Fix by stopping and disabling bulk receiving in usbredir_ep_info() when max_packet_size is set to 0. Add post-load check, and assert() for the invariant. Fixes: CVE-2026-63319 Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3995 Reported-by: Tristan @TristanInSec Signed-off-by: Marc-Andr=C3=A9 Lureau Reviewed-by: Thomas Huth --- hw/usb/redirect.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/hw/usb/redirect.c b/hw/usb/redirect.c index 284bcbdb34d..dfd9e8bb50c 100644 --- a/hw/usb/redirect.c +++ b/hw/usb/redirect.c @@ -690,6 +690,7 @@ static void usbredir_buffered_bulk_in_complete_ftdi(USB= RedirDevice *dev, struct buf_packet *bulkp; int count; =20 + assert(maxp !=3D 0); while ((bulkp =3D QTAILQ_FIRST(&dev->endpoint[EP2I(ep)].bufpq)) && p->actual_length < p->iov.size && p->status =3D=3D USB_RET_SUCC= ESS) { if (bulkp->len < 2) { @@ -739,6 +740,7 @@ static void usbredir_handle_buffered_bulk_in_data(USBRe= dirDevice *dev, .stream_id =3D 0, .no_transfers =3D 5, }; + assert(dev->endpoint[EP2I(ep)].max_packet_size !=3D 0); /* Round bytes_per_transfer up to a multiple of max_packet_size */ bpt =3D 512 + dev->endpoint[EP2I(ep)].max_packet_size - 1; bpt /=3D dev->endpoint[EP2I(ep)].max_packet_size; @@ -793,6 +795,7 @@ static void usbredir_handle_bulk_data(USBRedirDevice *d= ev, USBPacket *p, } =20 if (dev->endpoint[EP2I(ep)].bulk_receiving_enabled) { + assert(maxp !=3D 0); if (size !=3D 0 && (size % maxp) =3D=3D 0) { usbredir_handle_buffered_bulk_in_data(dev, p, ep); return; @@ -1796,6 +1799,17 @@ static void usbredir_ep_info(void *priv, if (usbredirparser_peer_has_cap(dev->parser, usb_redir_cap_ep_info_max_packet_size= )) { dev->endpoint[i].max_packet_size =3D ep_info->max_packet_size[= i]; + if (ep_info->max_packet_size[i] =3D=3D 0 && + dev->endpoint[i].bulk_receiving_enabled) { + USBPacket *p =3D dev->endpoint[i].pending_async_packet; + usbredir_stop_bulk_receiving(dev, I2EP(i)); + dev->endpoint[i].bulk_receiving_enabled =3D 0; + if (p !=3D NULL) { + dev->endpoint[i].pending_async_packet =3D NULL; + p->status =3D USB_RET_IOERROR; + usb_packet_complete(&dev->dev, p); + } + } } #if USBREDIR_VERSION >=3D 0x000700 if (usbredirparser_peer_has_cap(dev->parser, @@ -2156,6 +2170,7 @@ static void usbredir_buffered_bulk_packet(void *priv,= uint64_t id, } =20 /* Data must be in maxp chunks for buffered_bulk_add_*_data_to_packet = */ + assert(dev->endpoint[EP2I(ep)].max_packet_size !=3D 0); len =3D dev->endpoint[EP2I(ep)].max_packet_size; status =3D usb_redir_success; free_on_destroy =3D NULL; @@ -2239,6 +2254,15 @@ static int usbredir_post_load(void *priv, int versio= n_id) usbredir_setup_usb_eps(dev); usbredir_check_bulk_receiving(dev); =20 + for (int i =3D 0; i < MAX_ENDPOINTS; i++) { + if (dev->endpoint[i].bulk_receiving_started && + dev->endpoint[i].max_packet_size =3D=3D 0) { + error_report("usbredir: endpoint %d has bulk receiving started= " + "with zero max_packet_size", i); + return -EINVAL; + } + } + return 0; } =20 --=20 2.55.0