From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	sashiko-bot@kernel.org,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: [PATCH 5.15 020/272] Input: synaptics-rmi4 - zero report size on F54 work error
Date: Thu, 20 Aug 2026 16:53:24 +0200
Message-ID: <20260820145231.839559704@linuxfoundation.org>
In-Reply-To: <20260820145231.229664293@linuxfoundation.org>
References: <20260820145231.229664293@linuxfoundation.org>
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5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>

commit dc76c3c8e8ad09362b8c1561f3928288c15cba2e upstream.

In rmi_f54_work(), if an error occurs during report request or command
verification, the code jumped directly to the 'error' label, bypassing
the 'abort' label where f54->report_size was normally zeroed out.

This left f54->report_size containing its previous successful payload
size. If a user then altered the V4L2 format to a smaller size, and a
subsequent run failed, rmi_f54_buffer_queue() would copy the stale,
larger payload size into the shrunken V4L2 buffer, causing a heap
buffer overflow.

Fix this by merging the 'abort' and 'error' labels into a single 'out'
exit path, and ensuring that f54->report_size is always set to 0 on
failure by checking for error and zeroing the local report_size first.

Fixes: 3a762dbd5347 ("[media] Input: synaptics-rmi4 - add support for F54 diagnostics")
Cc: stable@vger.kernel.org
Reported-by: sashiko-bot@kernel.org
Assisted-by: Antigravity:gemini-3.5-flash
Link: https://patch.msgid.link/20260626051802.4033172-2-dmitry.torokhov@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/input/rmi4/rmi_f54.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- a/drivers/input/rmi4/rmi_f54.c
+++ b/drivers/input/rmi4/rmi_f54.c
@@ -547,7 +547,7 @@ static void rmi_f54_work(struct work_str
 		dev_err(&fn->dev, "Bad report size, report type=%d\n",
 				f54->report_type);
 		error = -EINVAL;
-		goto error;     /* retry won't help */
+		goto out;     /* retry won't help */
 	}
 
 	/*
@@ -558,7 +558,7 @@ static void rmi_f54_work(struct work_str
 			 &command);
 	if (error) {
 		dev_err(&fn->dev, "Failed to read back command\n");
-		goto error;
+		goto out;
 	}
 	if (command & F54_GET_REPORT) {
 		if (time_after(jiffies, f54->timeout)) {
@@ -566,7 +566,7 @@ static void rmi_f54_work(struct work_str
 			error = -ETIMEDOUT;
 		}
 		report_size = 0;
-		goto error;
+		goto out;
 	}
 
 	rmi_dbg(RMI_DEBUG_FN, &fn->dev, "Get report command completed, reading data\n");
@@ -581,7 +581,7 @@ static void rmi_f54_work(struct work_str
 					fifo, sizeof(fifo));
 		if (error) {
 			dev_err(&fn->dev, "Failed to set fifo start offset\n");
-			goto abort;
+			goto out;
 		}
 
 		error = rmi_read_block(fn->rmi_dev, fn->fd.data_base_addr +
@@ -590,16 +590,16 @@ static void rmi_f54_work(struct work_str
 		if (error) {
 			dev_err(&fn->dev, "%s: read [%d bytes] returned %d\n",
 				__func__, size, error);
-			goto abort;
+			goto out;
 		}
 	}
 
-abort:
-	f54->report_size = error ? 0 : report_size;
-error:
+out:
 	if (error)
 		report_size = 0;
 
+	f54->report_size = report_size;
+
 	if (report_size == 0 && !error) {
 		queue_delayed_work(f54->workqueue, &f54->work,
 				   msecs_to_jiffies(1));