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[54.252.206.51]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-81fa12b3165sm4063839b3a.60.2026.01.17.01.46.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 17 Jan 2026 01:46:37 -0800 (PST) From: Weigang He To: mathias.nyman@intel.com, gregkh@linuxfoundation.org Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Weigang He Subject: [PATCH] usb: xhci: fix missing null termination after copy_from_user() Date: Sat, 17 Jan 2026 09:46:31 +0000 Message-Id: <20260117094631.504232-1-geoffreyhe2@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The buffer 'buf' is filled by copy_from_user() but is not properly null-terminated before being used with strncmp(). If userspace provides fewer than 10 bytes, strncmp() may read beyond the copied data into uninitialized stack memory. Add explicit null termination after copy_from_user() to ensure the buffer is always a valid C string before string operations. Fixes: 87a03802184c ("xhci: debugfs: add debugfs interface to enable compli= ance mode for a port") Cc: stable@vger.kernel.org Signed-off-by: Weigang He --- drivers/usb/host/xhci-debugfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/usb/host/xhci-debugfs.c b/drivers/usb/host/xhci-debugf= s.c index c1eb1036ede95..1e2350de77775 100644 --- a/drivers/usb/host/xhci-debugfs.c +++ b/drivers/usb/host/xhci-debugfs.c @@ -347,11 +347,13 @@ static ssize_t xhci_port_write(struct file *file, co= nst char __user *ubuf, struct xhci_port *port =3D s->private; struct xhci_hcd *xhci =3D hcd_to_xhci(port->rhub->hcd); char buf[32]; + size_t len =3D min_t(size_t, sizeof(buf) - 1, count); u32 portsc; unsigned long flags; =20 - if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count))) + if (copy_from_user(&buf, ubuf, len)) return -EFAULT; + buf[len] =3D '\0'; =20 if (!strncmp(buf, "compliance", 10)) { /* If CTC is clear, compliance is enabled by default */ --=20 2.34.1