[PATCH 4/4] Strict XenStore entry parsing

From: Demi Marie Obenour <demi@invisiblethingslab.com>
To: Dwaipayan Ray <dwaipayanray1@gmail.com>,
	Lukas Bulwahn <lukas.bulwahn@gmail.com>,
	Joe Perches <joe@perches.com>, Jonathan Corbet <corbet@lwn.net>,
	Federico Vaga <federico.vaga@vaga.pv.it>,
	Juergen Gross <jgross@suse.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
	Lee Jones <lee@kernel.org>, Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Petr Mladek <pmladek@suse.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Demi Marie Obenour <demi@invisiblethingslab.com>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	xen-devel@lists.xenproject.org
Subject: [PATCH 4/4] Strict XenStore entry parsing
Date: Fri,  9 Jun 2023 22:57:59 -0400	[thread overview]
Message-ID: <20230610025759.1813-4-demi@invisiblethingslab.com> (raw)
In-Reply-To: <20230610025759.1813-1-demi@invisiblethingslab.com>

This uses the newly-introduced strict version of sscanf().

Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
---
 drivers/xen/xenbus/xenbus_xs.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 12e02eb01f5991b31db451cc57037205359b347f..88e94269c9221d16d1a97e59399058e870675729 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -569,16 +569,20 @@ int xenbus_scanf(struct xenbus_transaction t,
 		 const char *dir, const char *node, const char *fmt, ...)
 {
 	va_list ap;
-	int ret;
+	int ret = 0;
+	unsigned int len;
 	char *val;
 
-	val = xenbus_read(t, dir, node, NULL);
+	val = xenbus_read(t, dir, node, &len);
 	if (IS_ERR(val))
 		return PTR_ERR(val);
+	if (strlen(val) != len)
+		goto bad;
 
 	va_start(ap, fmt);
-	ret = vsscanf(val, fmt, ap);
+	ret = vsscanf_strict(val, fmt, ap);
 	va_end(ap);
+bad:
 	kfree(val);
 	/* Distinctive errno. */
 	if (ret == 0)
@@ -636,15 +640,18 @@ int xenbus_gather(struct xenbus_transaction t, const char *dir, ...)
 	while (ret == 0 && (name = va_arg(ap, char *)) != NULL) {
 		const char *fmt = va_arg(ap, char *);
 		void *result = va_arg(ap, void *);
+		unsigned len;
 		char *p;
 
-		p = xenbus_read(t, dir, name, NULL);
+		p = xenbus_read(t, dir, name, &len);
 		if (IS_ERR(p)) {
 			ret = PTR_ERR(p);
 			break;
 		}
-		if (fmt) {
-			if (sscanf(p, fmt, result) == 0)
+		if (strlen(p) != len)
+			ret = -EINVAL;
+		else if (fmt) {
+			if (sscanf_strict(p, fmt, result) <= 0)
 				ret = -EINVAL;
 			kfree(p);
 		} else
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab

