mac80211_hwsim: Use kstrndup() in place of kasprintf()

syzbot reports a warning:

precision 33020 too large
WARNING: CPU: 0 PID: 9618 at lib/vsprintf.c:2471 set_precision+0x150/0x180 lib/vsprintf.c:2471
 vsnprintf+0xa7b/0x19a0 lib/vsprintf.c:2547
 kvasprintf+0xb2/0x170 lib/kasprintf.c:22
 kasprintf+0xbb/0xf0 lib/kasprintf.c:59
 hwsim_del_radio_nl+0x63a/0x7e0 drivers/net/wireless/mac80211_hwsim.c:3625
 genl_family_rcv_msg_doit net/netlink/genetlink.c:672 [inline]
 ...
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Thus it seems that kasprintf() with "%.*s" format can not be used for
duplicating a string with arbitrary length. Replace it with kstrndup().

Note that later this string is limited to NL80211_WIPHY_NAME_MAXLEN == 64,
but the code is simpler this way.

Reported-by: syzbot+6693adf1698864d21734@syzkaller.appspotmail.com
Reported-by: syzbot+a4aee3f42d7584d76761@syzkaller.appspotmail.com
Cc: stable@kernel.org
Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Link: https://lore.kernel.org/r/20200410123257.14559-1-tuomas.tynkkynen@iki.fi
[johannes: add note about length limit]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 7fe8207db6ae9d7dd1c99c302116e7293fe36426..7c4b7c31d07ab88e86a41dc5e1491b6edff1bef5 100644 (file)
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -3669,9 +3669,9 @@ static int hwsim_new_radio_nl(struct sk_buff *msg, struct genl_info *info)
        }
 
        if (info->attrs[HWSIM_ATTR_RADIO_NAME]) {
-               hwname = kasprintf(GFP_KERNEL, "%.*s",
-                                  nla_len(info->attrs[HWSIM_ATTR_RADIO_NAME]),
-                                  (char *)nla_data(info->attrs[HWSIM_ATTR_RADIO_NAME]));
+               hwname = kstrndup((char *)nla_data(info->attrs[HWSIM_ATTR_RADIO_NAME]),
+                                 nla_len(info->attrs[HWSIM_ATTR_RADIO_NAME]),
+                                 GFP_KERNEL);
                if (!hwname)
                        return -ENOMEM;
                param.hwname = hwname;
@@ -3691,9 +3691,9 @@ static int hwsim_del_radio_nl(struct sk_buff *msg, struct genl_info *info)
        if (info->attrs[HWSIM_ATTR_RADIO_ID]) {
                idx = nla_get_u32(info->attrs[HWSIM_ATTR_RADIO_ID]);
        } else if (info->attrs[HWSIM_ATTR_RADIO_NAME]) {
-               hwname = kasprintf(GFP_KERNEL, "%.*s",
-                                  nla_len(info->attrs[HWSIM_ATTR_RADIO_NAME]),
-                                  (char *)nla_data(info->attrs[HWSIM_ATTR_RADIO_NAME]));
+               hwname = kstrndup((char *)nla_data(info->attrs[HWSIM_ATTR_RADIO_NAME]),
+                                 nla_len(info->attrs[HWSIM_ATTR_RADIO_NAME]),
+                                 GFP_KERNEL);
                if (!hwname)
                        return -ENOMEM;
        } else