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Berrange" Subject: [PATCH v2] hw/usb/dev-uas: Fix guest-triggerable heap OOB access Date: Mon, 20 Jul 2026 15:48:09 +0200 Message-ID: <20260720134809.573757-1-thuth@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: permerror client-ip=170.10.129.124; envelope-from=thuth@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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Thomas Huth The stream ID is under control of the guest, and some spots in the code currently use it for indexing into the status3[] array without checking it for being in range first, so the code accesses the heap beyond the limit of the status3 array. Since our status delivery code depends on having a valid stream ID, we must not try to generate a fake sense code in this situation. Simply log a guest error and return early in usb_uas_command(). And to make sure that we really cannot access the status3[] array beyond its limit anymore, add some assert() statements in the affected functions, too. Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3612 Reported-by: Reported-by: huntr bubble Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3986 Reported-by: Tristan Madani Suggested-by: Peter Maydell Signed-off-by: Thomas Huth --- v2: Refuse illegal tags already in usb_uas_command() hw/usb/dev-uas.c | 29 ++++++++++++++++++++--------- 1 file changed, 20 insertions(+), 9 deletions(-) diff --git a/hw/usb/dev-uas.c b/hw/usb/dev-uas.c index 8576dfec96f..963c0433b38 100644 --- a/hw/usb/dev-uas.c +++ b/hw/usb/dev-uas.c @@ -362,6 +362,7 @@ static void usb_uas_send_status_bh(void *opaque) while ((st = QTAILQ_FIRST(&uas->results)) != NULL) { if (uas_using_streams(uas)) { + assert(st->stream <= UAS_MAX_STREAMS); p = uas->status3[st->stream]; uas->status3[st->stream] = NULL; } else { @@ -383,8 +384,14 @@ static void usb_uas_send_status_bh(void *opaque) static void usb_uas_queue_status(UASDevice *uas, UASStatus *st, int length) { - USBPacket *p = uas_using_streams(uas) ? - uas->status3[st->stream] : uas->status2; + USBPacket *p; + + if (uas_using_streams(uas)) { + assert(st->stream <= UAS_MAX_STREAMS); + p = uas->status3[st->stream]; + } else { + p = uas->status2; + } st->length += length; QTAILQ_INSERT_TAIL(&uas->results, st, next); @@ -700,14 +707,22 @@ static void usb_uas_command(UASDevice *uas, uas_iu *iu) uint16_t tag = be16_to_cpu(iu->hdr.tag); size_t cdb_len = sizeof(iu->command.cdb) + iu->command.add_cdb_length; + if (uas_using_streams(uas) && tag > UAS_MAX_STREAMS) { + /* + * Our status delivery only works with valid tags, so in case the + * stream ID is out of bounds, we have to return immediately here + * without sending a fake sense_code_INVALID_TAG to the guest. + */ + qemu_log_mask(LOG_GUEST_ERROR, + "invalid tag 0x%x for USB UAS command\n", tag); + return; + } + if (iu->command.add_cdb_length > 0) { qemu_log_mask(LOG_UNIMP, "additional adb length not yet supported\n"); goto unsupported_len; } - if (uas_using_streams(uas) && tag > UAS_MAX_STREAMS) { - goto invalid_tag; - } req = usb_uas_find_request(uas, tag); if (req) { goto overlapped_tag; @@ -744,10 +759,6 @@ unsupported_len: usb_uas_queue_fake_sense(uas, tag, sense_code_INVALID_PARAM_VALUE); return; -invalid_tag: - usb_uas_queue_fake_sense(uas, tag, sense_code_INVALID_TAG); - return; - overlapped_tag: usb_uas_queue_fake_sense(uas, tag, sense_code_OVERLAPPED_COMMANDS); return; -- 2.55.0