[PATCH 4.9 21/96] cfg80211: limit wiphy names to 128 bytes

[Greg Kroah-Hartman]

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

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

From: Johannes Berg <johannes.berg@xxxxxxxxx>

commit a7cfebcb7594a24609268f91299ab85ba064bf82 upstream.

There's currently no limit on wiphy names, other than netlink
message size and memory limitations, but that causes issues when,
for example, the wiphy name is used in a uevent, e.g. in rfkill
where we use the same name for the rfkill instance, and then the
buffer there is "only" 2k for the environment variables.

This was reported by syzkaller, which used a 4k name.

Limit the name to something reasonable, I randomly picked 128.

Reported-by: syzbot+230d9e642a85d3fec29c@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/uapi/linux/nl80211.h |    2 ++
 net/wireless/core.c          |    3 +++
 2 files changed, 5 insertions(+)

--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -2379,6 +2379,8 @@ enum nl80211_attrs {
 #define NL80211_ATTR_KEYS NL80211_ATTR_KEYS
 #define NL80211_ATTR_FEATURE_FLAGS NL80211_ATTR_FEATURE_FLAGS
 
+#define NL80211_WIPHY_NAME_MAXLEN		128
+
 #define NL80211_MAX_SUPP_RATES			32
 #define NL80211_MAX_SUPP_HT_RATES		77
 #define NL80211_MAX_SUPP_REG_RULES		64
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -95,6 +95,9 @@ static int cfg80211_dev_check_name(struc
 
 	ASSERT_RTNL();
 
+	if (strlen(newname) > NL80211_WIPHY_NAME_MAXLEN)
+		return -EINVAL;
+
 	/* prohibit calling the thing phy%d when %d is not its number */
 	sscanf(newname, PHY_NAME "%d%n", &wiphy_idx, &taken);
 	if (taken == strlen(newname) && wiphy_idx != rdev->wiphy_idx) {