diff mbox series

[4/4] Strict XenStore entry parsing

Message ID 20230610025759.1813-4-demi@invisiblethingslab.com (mailing list archive)
State New, archived
Headers show
Series [1/4] Rip out simple_strtoll() | expand

Commit Message

Demi Marie Obenour June 10, 2023, 2:57 a.m. UTC 
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(-)

Comments

Matthew Wilcox June 10, 2023, 3:26 a.m. UTC | #1 
On Fri, Jun 09, 2023 at 10:57:59PM -0400, Demi Marie Obenour wrote:
> This uses the newly-introduced strict version of sscanf().

I can see that.  Why does it do that?

Documentation/process/5.Posting.rst

(in general, there is a lack of detail across all four of these patches
justifying why any of this work is being done.  it isn't obvious to me
why skipping leading whitespace is bad in this context)
diff mbox series

Patch

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