[PATCH 5.6 54/71] mac80211_hwsim: Use kstrndup() in place of kasprintf()

From: Greg Kroah-Hartman
Date: Mon Apr 20 2020 - 08:56:41 EST


From: Tuomas Tynkkynen <tuomas.tynkkynen@xxxxxx>

commit 7ea862048317aa76d0f22334202779a25530980c upstream.

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@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+a4aee3f42d7584d76761@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxx
Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@xxxxxx>
Link: https://lore.kernel.org/r/20200410123257.14559-1-tuomas.tynkkynen@xxxxxx
[johannes: add note about length limit]
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/net/wireless/mac80211_hwsim.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -3600,9 +3600,9 @@ static int hwsim_new_radio_nl(struct sk_
}

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;
@@ -3622,9 +3622,9 @@ static int hwsim_del_radio_nl(struct sk_
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