FAILED: patch "[PATCH] USB: serial: cypress_m8: fix memory corruption with small" failed to apply to 6.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.18-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 <stable@vger.kernel.org>.

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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x e1a9d791fd66ab2431b9e6f6f835823809869047
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026060436-outcome-uptight-239a@gregkh' --subject-prefix 'PATCH 6.18.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 <johan@kernel.org>
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.

Fixes: 3416eaa1f8f8 ("USB: cypress_m8: Packet format is separate from characteristic size")
Cc: stable@vger.kernel.org	# 2.6.26
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index afff1a0f4298..0b8a4e9d7bc5 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -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;