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Date: Thu, 4 Jan 2024 16:30:26 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: alexis.lothore@...tlin.com
Cc: ajay.kathat@...rochip.com, claudiu.beznea@...on.dev, kvalo@...nel.org,
linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
thomas.petazzoni@...tlin.com
Subject: Re: [PATCH 2/2] wifi: wilc1000: fix RCU usage in connect path
Le 04/01/2024 à 15:39, Alexis Lothoré a écrit :
> From: Alexis Lothoré <alexis.lothore-LDxbnhwyfcJBDgjK7y7TUQ@...lic.gmane.org>
>
> With lockdep enabled, calls to the connect function from cfg802.11 layer
> lead to the following warning:
>
> =============================
> WARNING: suspicious RCU usage
> 6.7.0-rc1-wt+ #333 Not tainted
> -----------------------------
> drivers/net/wireless/microchip/wilc1000/hif.c:386
> suspicious rcu_dereference_check() usage!
> [...]
> stack backtrace:
> CPU: 0 PID: 100 Comm: wpa_supplicant Not tainted 6.7.0-rc1-wt+ #333
> Hardware name: Atmel SAMA5
> unwind_backtrace from show_stack+0x18/0x1c
> show_stack from dump_stack_lvl+0x34/0x48
> dump_stack_lvl from wilc_parse_join_bss_param+0x7dc/0x7f4
> wilc_parse_join_bss_param from connect+0x2c4/0x648
> connect from cfg80211_connect+0x30c/0xb74
> cfg80211_connect from nl80211_connect+0x860/0xa94
> nl80211_connect from genl_rcv_msg+0x3fc/0x59c
> genl_rcv_msg from netlink_rcv_skb+0xd0/0x1f8
> netlink_rcv_skb from genl_rcv+0x2c/0x3c
> genl_rcv from netlink_unicast+0x3b0/0x550
> netlink_unicast from netlink_sendmsg+0x368/0x688
> netlink_sendmsg from ____sys_sendmsg+0x190/0x430
> ____sys_sendmsg from ___sys_sendmsg+0x110/0x158
> ___sys_sendmsg from sys_sendmsg+0xe8/0x150
> sys_sendmsg from ret_fast_syscall+0x0/0x1c
>
> This warning is emitted because in the connect path, when trying to parse
> target BSS parameters, we dereference a RCU pointer whithout being in RCU
> critical section.
> Fix RCU dereference usage by moving it to a RCU read critical section. To
> avoid wrapping the whole wilc_parse_join_bss_param under the critical
> section, just use the critical section to copy ies data
>
> Fixes: c460495ee072 ("staging: wilc1000: fix incorrent type in initializer")
> Signed-off-by: Alexis Lothoré <alexis.lothore-LDxbnhwyfcJBDgjK7y7TUQ@...lic.gmane.org>
> ---
> drivers/net/wireless/microchip/wilc1000/hif.c | 35 ++++++++++++-------
> 1 file changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/wireless/microchip/wilc1000/hif.c b/drivers/net/wireless/microchip/wilc1000/hif.c
> index 6f1218a51061..806b7337b5ae 100644
> --- a/drivers/net/wireless/microchip/wilc1000/hif.c
> +++ b/drivers/net/wireless/microchip/wilc1000/hif.c
> @@ -377,38 +377,48 @@ struct wilc_join_bss_param *
> wilc_parse_join_bss_param(struct cfg80211_bss *bss,
> struct cfg80211_crypto_settings *crypto)
> {
> - const struct cfg80211_bss_ies *ies = rcu_dereference(bss->ies);
> - const u8 *tim_elm, *ssid_elm, *rates_ie, *supp_rates_ie;
> + const u8 *ies_data, *tim_elm, *ssid_elm, *rates_ie, *supp_rates_ie;
> const u8 *ht_ie, *wpa_ie, *wmm_ie, *rsn_ie;
> struct ieee80211_p2p_noa_attr noa_attr;
> + const struct cfg80211_bss_ies *ies;
> struct wilc_join_bss_param *param;
> - u8 rates_len = 0;
> + u8 rates_len = 0, ies_len;
> int ret;
>
> param = kzalloc(sizeof(*param), GFP_KERNEL);
> if (!param)
> return NULL;
>
> + rcu_read_lock();
> + ies = rcu_dereference(bss->ies);
> + ies_data = kmemdup(ies->data, ies->len, GFP_ATOMIC);
Is it mandatory to have GFP_ATOMIC here?
If yes, then some other drivers may need to be fixed (at least [1]).
> + if (!ies_data) {
> + rcu_read_unlock();
'param' allocated just a few lines above is leaking now.
CJ
[1]:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/pci/p2pdma.c#n660
> + return NULL;
> + }
> + ies_len = ies->len;
> + rcu_read_unlock();
> +
> param->beacon_period = cpu_to_le16(bss->beacon_interval);
> param->cap_info = cpu_to_le16(bss->capability);
> param->bss_type = WILC_FW_BSS_TYPE_INFRA;
> param->ch = ieee80211_frequency_to_channel(bss->channel->center_freq);
> ether_addr_copy(param->bssid, bss->bssid);
>
> - ssid_elm = cfg80211_find_ie(WLAN_EID_SSID, ies->data, ies->len);
> + ssid_elm = cfg80211_find_ie(WLAN_EID_SSID, ies_data, ies_len);
> if (ssid_elm) {
> if (ssid_elm[1] <= IEEE80211_MAX_SSID_LEN)
> memcpy(param->ssid, ssid_elm + 2, ssid_elm[1]);
> }
>
> - tim_elm = cfg80211_find_ie(WLAN_EID_TIM, ies->data, ies->len);
> + tim_elm = cfg80211_find_ie(WLAN_EID_TIM, ies_data, ies_len);
> if (tim_elm && tim_elm[1] >= 2)
> param->dtim_period = tim_elm[3];
>
> memset(param->p_suites, 0xFF, 3);
> memset(param->akm_suites, 0xFF, 3);
>
> - rates_ie = cfg80211_find_ie(WLAN_EID_SUPP_RATES, ies->data, ies->len);
> + rates_ie = cfg80211_find_ie(WLAN_EID_SUPP_RATES, ies_data, ies_len);
> if (rates_ie) {
> rates_len = rates_ie[1];
> if (rates_len > WILC_MAX_RATES_SUPPORTED)
> @@ -419,7 +429,7 @@ wilc_parse_join_bss_param(struct cfg80211_bss *bss,
>
> if (rates_len < WILC_MAX_RATES_SUPPORTED) {
> supp_rates_ie = cfg80211_find_ie(WLAN_EID_EXT_SUPP_RATES,
> - ies->data, ies->len);
> + ies_data, ies_len);
> if (supp_rates_ie) {
> u8 ext_rates = supp_rates_ie[1];
>
> @@ -434,11 +444,11 @@ wilc_parse_join_bss_param(struct cfg80211_bss *bss,
> }
> }
>
> - ht_ie = cfg80211_find_ie(WLAN_EID_HT_CAPABILITY, ies->data, ies->len);
> + ht_ie = cfg80211_find_ie(WLAN_EID_HT_CAPABILITY, ies_data, ies_len);
> if (ht_ie)
> param->ht_capable = true;
>
> - ret = cfg80211_get_p2p_attr(ies->data, ies->len,
> + ret = cfg80211_get_p2p_attr(ies_data, ies_len,
> IEEE80211_P2P_ATTR_ABSENCE_NOTICE,
> (u8 *)&noa_attr, sizeof(noa_attr));
> if (ret > 0) {
> @@ -462,7 +472,7 @@ wilc_parse_join_bss_param(struct cfg80211_bss *bss,
> }
> wmm_ie = cfg80211_find_vendor_ie(WLAN_OUI_MICROSOFT,
> WLAN_OUI_TYPE_MICROSOFT_WMM,
> - ies->data, ies->len);
> + ies_data, ies_len);
> if (wmm_ie) {
> struct ieee80211_wmm_param_ie *ie;
>
> @@ -477,13 +487,13 @@ wilc_parse_join_bss_param(struct cfg80211_bss *bss,
>
> wpa_ie = cfg80211_find_vendor_ie(WLAN_OUI_MICROSOFT,
> WLAN_OUI_TYPE_MICROSOFT_WPA,
> - ies->data, ies->len);
> + ies_data, ies_len);
> if (wpa_ie) {
> param->mode_802_11i = 1;
> param->rsn_found = true;
> }
>
> - rsn_ie = cfg80211_find_ie(WLAN_EID_RSN, ies->data, ies->len);
> + rsn_ie = cfg80211_find_ie(WLAN_EID_RSN, ies_data, ies_len);
> if (rsn_ie) {
> int rsn_ie_len = sizeof(struct element) + rsn_ie[1];
> int offset = 8;
> @@ -517,6 +527,7 @@ wilc_parse_join_bss_param(struct cfg80211_bss *bss,
> param->akm_suites[i] = crypto->akm_suites[i] & 0xFF;
> }
>
> + kfree(ies_data);
> return (void *)param;
> }
>
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