FAILED: patch "[PATCH] HID: magicmouse: prevent unbounded recursion in" failed to apply to 6.6-stable tree

[<gregkh@linuxfoundation.org>]

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 <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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x db8d634128d2ba88d79c0b601e983ebe14bb0519
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026082525-parabola-duplicate-d396@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From db8d634128d2ba88d79c0b601e983ebe14bb0519 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jose=20Villase=C3=B1or=20Montfort?= <pepemontfort@gmail.com>
Date: Tue, 14 Jul 2026 23:35:26 -0600
Subject: [PATCH] HID: magicmouse: prevent unbounded recursion in
 magicmouse_raw_event()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

magicmouse_raw_event() handles DOUBLE_REPORT_ID (0xf7) packets, which pack
two touch reports into one, by splitting the packet and calling itself on
each half. The only guard against runaway recursion is a "size < 1" check,
which stops zero-sized calls but does not bound the recursion depth.

A malicious HID device that matches this driver can send a report starting
with DOUBLE_REPORT_ID and filled with the sequence [0xf7, 0x00]. Each level
consumes two bytes and recurses on the remainder, so an incoming report of
up to HID_MAX_BUFFER_SIZE (16 KiB) drives roughly 8000 nested calls. That
easily exhausts the 16 KiB kernel stack, leading to a stack overflow: a
panic with CONFIG_VMAP_STACK, or memory corruption without it.

A double report only ever wraps two normal reports; it is never
legitimately nested. Refuse to re-enter the DOUBLE_REPORT_ID case from a
recursive call so the recursion depth is bounded to two, while all valid
packets keep being parsed exactly as before.

Fixes: a462230e16ac ("HID: magicmouse: enable Magic Trackpad support")
Link: https://lore.kernel.org/linux-input/20260706181347.700DB1F00A3F@smtp.kernel.org/
Cc: stable@vger.kernel.org
Signed-off-by: Jose Villaseñor Montfort <pepemontfort@gmail.com>
Reviewed-by: Alec Hall <signshop.alec@gmail.com>
Tested-by: Alec Hall <signshop.alec@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index 802a3479e24b..97562765a01d 100644
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c
@@ -383,8 +383,8 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
 	}
 }
 
-static int magicmouse_raw_event(struct hid_device *hdev,
-		struct hid_report *report, u8 *data, int size)
+static int __magicmouse_raw_event(struct hid_device *hdev,
+		struct hid_report *report, u8 *data, int size, bool nested)
 {
 	struct magicmouse_sc *msc = hid_get_drvdata(hdev);
 	struct input_dev *input = msc->input;
@@ -495,6 +495,15 @@ static int magicmouse_raw_event(struct hid_device *hdev,
 		 * packet.
 		 */
 
+		/*
+		 * A double report only ever wraps two normal reports, so it is
+		 * never nested. Refuse to recurse a second time; otherwise a
+		 * malicious device could chain DOUBLE_REPORT_ID packets to drive
+		 * unbounded recursion and overflow the kernel stack.
+		 */
+		if (nested)
+			return 0;
+
 		/* Ensure that we have at least 2 elements (report type and size) */
 		if (size < 2)
 			return 0;
@@ -506,9 +515,9 @@ static int magicmouse_raw_event(struct hid_device *hdev,
 			return 0;
 		}
 
-		magicmouse_raw_event(hdev, report, data + 2, data[1]);
-		magicmouse_raw_event(hdev, report, data + 2 + data[1],
-			size - 2 - data[1]);
+		__magicmouse_raw_event(hdev, report, data + 2, data[1], true);
+		__magicmouse_raw_event(hdev, report, data + 2 + data[1],
+			size - 2 - data[1], true);
 		return 0;
 	default:
 		return 0;
@@ -534,6 +543,12 @@ static int magicmouse_raw_event(struct hid_device *hdev,
 	return 1;
 }
 
+static int magicmouse_raw_event(struct hid_device *hdev,
+		struct hid_report *report, u8 *data, int size)
+{
+	return __magicmouse_raw_event(hdev, report, data, size, false);
+}
+
 static int magicmouse_event(struct hid_device *hdev, struct hid_field *field,
 		struct hid_usage *usage, __s32 value)
 {