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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1783958706; 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=IPwmvNgzpvqEs2n7dYPiWnQDbwjka8OPTrkMOq5/BEY=; b=PNsTYl/JzwnmqkbtAl+cCZMYD8IR2YxAIFcpuRGa/4WCj+rMMiv2+7N5c7B8AEpXsx33cM bitaBCyvWTcU14PqSGCOVij2Zs8jgqdvIrb6Cx+gWAq9Kragt1gPoakQxiT2TRxKs+uUAa H65RL2GsPJigvr5Q6KxuUhICRpmGkT4= X-MC-Unique: aZgzCPb5NMKcvswGzF-Flw-1 X-Mimecast-MFC-AGG-ID: aZgzCPb5NMKcvswGzF-Flw_1783958704 From: Thomas Huth To: qemu-devel@nongnu.org Cc: qemu-trivial@nongnu.org, Peter Maydell , Munkhbaatar Enkhbaatar , =?UTF-8?q?Daniel=20P=20=2E=20Berrang=C3=A9?= , qemu-stable@nongnu.org Subject: [PATCH] hw/usb/hcd-ohci: Make sure that ohci_service_ed_list() cannot loop forever Date: Mon, 13 Jul 2026 18:04:58 +0200 Message-ID: <20260713160458.343323-1-thuth@redhat.com> MIME-Version: 1.0 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; 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charset="utf-8" From: Thomas Huth The inner while loop in ohci_service_ed_list() could theoretically loop forever if a malicious guest prepares a set of bad descriptors. Add a check to the loop to avoid this situation. Reported-by: Feifan Qian Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3781 Signed-off-by: Thomas Huth Reviewed-by: Daniel P. Berrang=C3=A9 --- hw/usb/hcd-ohci.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c index 40ebafb4dd9..c4a9741bd42 100644 --- a/hw/usb/hcd-ohci.c +++ b/hw/usb/hcd-ohci.c @@ -28,6 +28,7 @@ #include "qemu/osdep.h" #include "hw/core/irq.h" #include "qapi/error.h" +#include "qemu/log.h" #include "qemu/module.h" #include "qemu/timer.h" #include "hw/usb/usb.h" @@ -1129,6 +1130,8 @@ static int ohci_service_ed_list(OHCIState *ohci, uint= 32_t head) return 0; } for (cur =3D head; cur && link_cnt++ < ED_LINK_LIMIT; cur =3D next_ed)= { + unsigned int ed_cnt =3D 0; + if (ohci_read_ed(ohci, cur, &ed)) { trace_usb_ohci_ed_read_error(cur); ohci_die(ohci); @@ -1172,6 +1175,13 @@ static int ohci_service_ed_list(OHCIState *ohci, uin= t32_t head) break; } } + + if (ed_cnt++ > ED_LINK_LIMIT) { + qemu_log_mask(LOG_GUEST_ERROR, + "ohci: Too many endpoint descriptors in loop= \n"); + ohci_die(ohci); + return 0; + } } =20 if (ohci_put_ed(ohci, cur, &ed)) { --=20 2.55.0