linux-kernel - [PATCH v2 2/2] fsi: sbefifo: Validate pending user write

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Message-Id: <20230911223809.3505431-3-ninad@linux.ibm.com>
Date:   Mon, 11 Sep 2023 17:38:09 -0500
From:   Ninad Palsule <ninad@...ux.ibm.com>
To:     jk@...abs.org, joel@....id.au, alistair@...ple.id.au,
        eajames@...ux.ibm.com, linux-fsi@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Cc:     Ninad Palsule <ninad@...ux.ibm.com>
Subject: [PATCH v2 2/2] fsi: sbefifo: Validate pending user write

This commit rejects user write operation if previous write operation is
still pending.

As per the current kernel driver design, write operation prepares a
buffer for FSI write, the actual FSI write is performed on next read
operation. There is a possibility of memory leak if buggy application
sends two back to back writes or two parallel writes.

Signed-off-by: Ninad Palsule <ninad@...ux.ibm.com>
---
 drivers/fsi/fsi-sbefifo.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
index a95b32461f8f..fc41cdd6e890 100644
--- a/drivers/fsi/fsi-sbefifo.c
+++ b/drivers/fsi/fsi-sbefifo.c
@@ -877,6 +877,12 @@ static ssize_t sbefifo_user_write(struct file *file, const char __user *buf,
 
 	mutex_lock(&user->file_lock);
 
+	/* Previous write is still in progress */
+	if (user->pending_cmd) {
+		mutex_unlock(&user->file_lock);
+		return -EALREADY;
+	}
+
 	/* Can we use the pre-allocate buffer ? If not, allocate */
 	if (len <= PAGE_SIZE)
 		user->pending_cmd = user->cmd_page;
-- 
2.39.2