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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1785429553; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=43P7i+PH3R93Mpl0oa1bgU1c/KBrgka5q7h3ziFXuLQ=; b=DSvtqeVNhXyJhk6mrtaZoxflvsKg6S8WqI8rDQS2d6hg+ufsMgp1ND/95KK1Gf7TbX0id2 e+CQ7d+aYn03Rijq5Wtc0itxFYoPrQ5x71cCaTT0peyt6DTUmzX/RQsdsE5gBXmLN8Ko4P uNCErUdhl/Hsqxkt/7ESrb4R5b/XxZo= X-MC-Unique: XUpUsWkAOdit2If3UqEP6w-1 X-Mimecast-MFC-AGG-ID: XUpUsWkAOdit2If3UqEP6w_1785429548 From: Thomas Huth To: qemu-devel@nongnu.org Cc: Feifan Qian , Peter Maydell , kraxel@redhat.com, qemu-trivial@nongnu.org, qemu-stable@nongnu.org, =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Subject: [PATCH] hw/usb/dev-uas: Don't abort if guest provided an undersized buffer for status Date: Thu, 30 Jul 2026 18:39:01 +0200 Message-ID: <20260730163901.1154791-1-thuth@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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=thuth@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: 1785429587968158500 Content-Type: text/plain; charset="utf-8" From: Thomas Huth QEMU currently aborts if the guest provides an undersized buffer for the status packet (8 bytes): hw/usb/core.c:623: usb_packet_copy: Assertion `p->actual_length + bytes <=3D iov->size' failed. If we hit this situation, log a guest error and continue by simply only providing the bytes that the guest asked for. (Note: This is e.g. similar to the UAS_PIPE_ID_COMMAND case that also clamps the length with: length =3D MIN(sizeof(iu), p->iov.size)) Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3900 Reported-by: Feifan Qian Signed-off-by: Thomas Huth --- hw/usb/dev-uas.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/hw/usb/dev-uas.c b/hw/usb/dev-uas.c index 963c0433b38..be8c3667e83 100644 --- a/hw/usb/dev-uas.c +++ b/hw/usb/dev-uas.c @@ -359,6 +359,7 @@ static void usb_uas_send_status_bh(void *opaque) UASDevice *uas =3D opaque; UASStatus *st; USBPacket *p; + uint32_t length; =20 while ((st =3D QTAILQ_FIRST(&uas->results)) !=3D NULL) { if (uas_using_streams(uas)) { @@ -373,7 +374,14 @@ static void usb_uas_send_status_bh(void *opaque) break; } =20 - usb_packet_copy(p, &st->status, st->length); + length =3D st->length; + if (length > p->iov.size) { + qemu_log_mask(LOG_GUEST_ERROR, + "usb uas: packet (%zd) too small for status (%d)= \n", + p->iov.size, length); + length =3D p->iov.size; + } + usb_packet_copy(p, &st->status, length); QTAILQ_REMOVE(&uas->results, st, next); g_free(st); =20 @@ -875,7 +883,14 @@ static void usb_uas_handle_data(USBDevice *dev, USBPac= ket *p) break; } } - usb_packet_copy(p, &st->status, st->length); + length =3D st->length; + if (length > p->iov.size) { + qemu_log_mask(LOG_GUEST_ERROR, + "usb uas: packet (%zd) too small for status (%d)= \n", + p->iov.size, length); + length =3D p->iov.size; + } + usb_packet_copy(p, &st->status, length); QTAILQ_REMOVE(&uas->results, st, next); g_free(st); break; --=20 2.55.0