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a=openpgp; fpr=87A9BD933F87C606D276F62DDAE8E10975969CE5 X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 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: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.852, 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: 1785930727100158500 A guest can send PC_to_RDR_XfrBlock USB messages faster than the async card backend can process them. When the pending_answers ring buffer (128 entries) fills, ccid_add_pending_answer() hits an assert() and crashes QEMU. The CCID spec (section 4) states that a slot can only accept one command at a time. A second command to a busy slot must be rejected with CMD_SLOT_BUSY (section 6.2.6). Enforce this by checking pending_answers_num before queuing a new APDU. When the slot is already busy, report ERROR_CMD_SLOT_BUSY and send a DataBlock error response back to the guest. Fixes: CVE-2026-18410 Fixes: 367071447ec5 ("usb-ccid: add CCID bus") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3997 Signed-off-by: Marc-Andr=C3=A9 Lureau --- hw/usb/dev-smartcard-reader.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/hw/usb/dev-smartcard-reader.c b/hw/usb/dev-smartcard-reader.c index 8241cd07648d..9fc6bbca0f2d 100644 --- a/hw/usb/dev-smartcard-reader.c +++ b/hw/usb/dev-smartcard-reader.c @@ -166,6 +166,7 @@ enum { ERROR_XFR_PARITY_ERROR =3D -3, ERROR_XFR_OVERRUN =3D -4, ERROR_HW_ERROR =3D -5, + ERROR_CMD_SLOT_BUSY =3D -32, }; =20 /* 6.2.6 RDR_to_PC_SlotStatus definitions */ @@ -945,6 +946,13 @@ static void ccid_on_apdu_from_guest(USBCCIDState *s, C= CID_XferBlock *recv) ccid_write_data_block_error(s, recv->hdr.bSlot, recv->hdr.bSeq); return; } + if (s->pending_answers_num > 0) { + DPRINTF(s, D_WARN, + "usb-ccid: slot already busy, rejecting apdu\n"); + ccid_report_error_failed(s, ERROR_CMD_SLOT_BUSY); + ccid_write_data_block_error(s, recv->hdr.bSlot, recv->hdr.bSeq); + return; + } len =3D le32_to_cpu(recv->hdr.dwLength); DPRINTF(s, 1, "%s: seq %d, len %u\n", __func__, recv->hdr.bSeq, len); --=20 2.55.0