[PATCH 4.9 125/177] cifs: small underflow in cnvrtDosUnixTm()

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>


[ Upstream commit 564277eceeca01e02b1ef3e141cfb939184601b4 ]

January is month 1.  There is no zero-th month.  If someone passes a
zero month then it means we read from one space before the start of the
total_days_of_prev_months[] array.

We may as well also be strict about days as well.

Fixes: 1bd5bbcb6531 ("[CIFS] Legacy time handling for Win9x and OS/2 part 1")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Steve French <smfrench@xxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/cifs/netmisc.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/cifs/netmisc.c
+++ b/fs/cifs/netmisc.c
@@ -980,10 +980,10 @@ struct timespec cnvrtDosUnixTm(__le16 le
 		cifs_dbg(VFS, "illegal hours %d\n", st->Hours);
 	days = sd->Day;
 	month = sd->Month;
-	if ((days > 31) || (month > 12)) {
+	if (days < 1 || days > 31 || month < 1 || month > 12) {
 		cifs_dbg(VFS, "illegal date, month %d day: %d\n", month, days);
-		if (month > 12)
-			month = 12;
+		days = clamp(days, 1, 31);
+		month = clamp(month, 1, 12);
 	}
 	month -= 1;
 	days += total_days_of_prev_months[month];