linux-kernel - [PATCH] mac80211_hwsim: Use kstrndup() in place of kasprintf()

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Date:   Fri, 10 Apr 2020 15:32:57 +0300
From:   Tuomas Tynkkynen <tuomas.tynkkynen@....fi>
To:     johannes@...solutions.net
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        syzbot+6693adf1698864d21734@...kaller.appspotmail.com,
        Tuomas Tynkkynen <tuomas.tynkkynen@....fi>, stable@...nel.org
Subject: [PATCH] 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().

Reported-by: syzbot+6693adf1698864d21734@...kaller.appspotmail.com
Cc: stable@...nel.org
Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@....fi>
---
Compile tested only.
---
 drivers/net/wireless/mac80211_hwsim.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 7fe8207db6ae..7c4b7c31d07a 100644
--- 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
-- 
2.17.1