FAILED: patch "[PATCH] USB: serial: cypress_m8: fix memory corruption with small" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x e1a9d791fd66ab2431b9e6f6f835823809869047
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026060437-pampers-nutrient-e02f@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e1a9d791fd66ab2431b9e6f6f835823809869047 Mon Sep 17 00:00:00 2001
From: Johan Hovold <[email protected]>
Date: Fri, 22 May 2026 12:16:21 +0200
Subject: [PATCH] USB: serial: cypress_m8: fix memory corruption with small
endpoint

Make sure that the interrupt-out endpoint max packet size is at least eight bytes to avoid user-controlled slab corruption or NULL-pointer dereference should a malicious device report a smaller size.

index afff1a0f4298..0b8a4e9d7bc5 100644
@@ -445,6 +445,14 @@ static int cypress_generic_port_probe(struct usb_serial_port *port)
 		return -ENODEV;
 	}
 
+	/*
+	 * The buffer must be large enough for the one or two-byte header (and
+	 * following data), but assume anything smaller than eight bytes is
+	 * broken.
+	 */
+	if (port->interrupt_out_size < 8)
+		return -EINVAL;
+
 	priv = kzalloc_obj(struct cypress_private);
 	if (!priv)
 		return -ENOMEM;

From: Johan Hovold <[email protected]>

[ Upstream commit e1a9d791fd66ab2431b9e6f6f835823809869047 ]

Make sure that the interrupt-out endpoint max packet size is at least eight bytes to avoid user-controlled slab corruption or NULL-pointer dereference should a malicious device report a smaller size.

---
 drivers/usb/serial/cypress_m8.c | 8 ++++++++
 1 file changed, 8 insertions(+)

index 1e0c028c5ec95f..e766b78f88634e 100644
@@ -448,6 +448,14 @@ static int cypress_generic_port_probe(struct usb_serial_port *port)
 		return -ENODEV;
 	}
 
+	/*
+	 * The buffer must be large enough for the one or two-byte header (and
+	 * following data), but assume anything smaller than eight bytes is
+	 * broken.
+	 */
+	if (port->interrupt_out_size < 8)
+		return -EINVAL;
+
 	priv = kzalloc(sizeof(struct cypress_private), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

2.53.0