* [PATCH] nl80211: take RCU read lock when calling ieee80211_bss_get_ie() [not found] ` <20180108100403.GA4715@light.dominikbrodowski.net> @ 2018-01-14 18:03 ` Dominik Brodowski 2018-01-14 21:58 ` Johannes Berg 0 siblings, 1 reply; 6+ messages in thread From: Dominik Brodowski @ 2018-01-14 18:03 UTC (permalink / raw) To: johannes.berg; +Cc: regressions, netdev, linux-wireless, linux-kernel As ieee80211_bss_get_ie() derefences an RCU, it needs to be called with rcu_read_lock held. Fixes: 44905265bc15 ("nl80211: don't expose wdev->ssid for most interfaces") Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> --- This patch fixes the regression I reported in the last couple of weeks for various v4.15-rcX revisions to netdev, where a "suspicious RCU usage" showed up in net/wireless/util.c:778. diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index 2b3dbcd40e46..1eecc249fb5e 100644 --- a/net/wireless/nl80211.c +++ b/net/wireless/nl80211.c @@ -2618,8 +2618,10 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag const u8 *ssid_ie; if (!wdev->current_bss) break; + rcu_read_lock(); ssid_ie = ieee80211_bss_get_ie(&wdev->current_bss->pub, WLAN_EID_SSID); + rcu_read_unlock(); if (!ssid_ie) break; if (nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2)) ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] nl80211: take RCU read lock when calling ieee80211_bss_get_ie() 2018-01-14 18:03 ` [PATCH] nl80211: take RCU read lock when calling ieee80211_bss_get_ie() Dominik Brodowski @ 2018-01-14 21:58 ` Johannes Berg 2018-01-14 22:22 ` [PATCH v2] " Dominik Brodowski 0 siblings, 1 reply; 6+ messages in thread From: Johannes Berg @ 2018-01-14 21:58 UTC (permalink / raw) To: Dominik Brodowski; +Cc: regressions, netdev, linux-wireless, linux-kernel Hi, > Fixes: 44905265bc15 ("nl80211: don't expose wdev->ssid for most interfaces") > Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> > --- > > This patch fixes the regression I reported in the last couple of weeks for > various v4.15-rcX revisions to netdev, where a "suspicious RCU usage" > showed up in net/wireless/util.c:778. Huh. You should added linux-wireless to those reports, I simply didn't see them! > diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c > index 2b3dbcd40e46..1eecc249fb5e 100644 > --- a/net/wireless/nl80211.c > +++ b/net/wireless/nl80211.c > @@ -2618,8 +2618,10 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag > const u8 *ssid_ie; > if (!wdev->current_bss) > break; > + rcu_read_lock(); > ssid_ie = ieee80211_bss_get_ie(&wdev->current_bss->pub, > WLAN_EID_SSID); > + rcu_read_unlock(); > if (!ssid_ie) > break; > if (nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2)) This uses the ssid_ie, so that doesn't really seem right? The protection should extend beyond the usage. johannes ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2] nl80211: take RCU read lock when calling ieee80211_bss_get_ie() 2018-01-14 21:58 ` Johannes Berg @ 2018-01-14 22:22 ` Dominik Brodowski 2018-01-14 22:40 ` Johannes Berg 0 siblings, 1 reply; 6+ messages in thread From: Dominik Brodowski @ 2018-01-14 22:22 UTC (permalink / raw) To: Johannes Berg; +Cc: regressions, netdev, linux-wireless, linux-kernel As ieee80211_bss_get_ie() derefences an RCU, it needs to be called with rcu_read_lock held. Fixes: 44905265bc15 ("nl80211: don't expose wdev->ssid for most interfaces") Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> --- > This uses the ssid_ie, so that doesn't really seem right? The > protection should extend beyond the usage. Indeed -- I had misread the code and hadn't thought of ssid_ie also needing the protection during its lifetime. So here's a new version 2 -- which I will only be able to test tomorrow, though... Thanks, Dominik diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index 2b3dbcd40e46..b53bd8db7974 100644 --- a/net/wireless/nl80211.c +++ b/net/wireless/nl80211.c @@ -2618,12 +2618,15 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag const u8 *ssid_ie; if (!wdev->current_bss) break; + rcu_read_lock(); ssid_ie = ieee80211_bss_get_ie(&wdev->current_bss->pub, WLAN_EID_SSID); if (!ssid_ie) - break; + goto nla_rcu_unlock; if (nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2)) - goto nla_put_failure_locked; + goto nla_put_failure_rcu_locked; + nla_rcu_unlock: + rcu_read_unlock(); break; } default: @@ -2635,6 +2638,8 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag genlmsg_end(msg, hdr); return 0; + nla_put_failure_rcu_locked: + rcu_read_unlock(); nla_put_failure_locked: wdev_unlock(wdev); nla_put_failure: ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2] nl80211: take RCU read lock when calling ieee80211_bss_get_ie() 2018-01-14 22:22 ` [PATCH v2] " Dominik Brodowski @ 2018-01-14 22:40 ` Johannes Berg 2018-01-15 7:12 ` [PATCH v3] " Dominik Brodowski 0 siblings, 1 reply; 6+ messages in thread From: Johannes Berg @ 2018-01-14 22:40 UTC (permalink / raw) To: Dominik Brodowski; +Cc: regressions, netdev, linux-wireless, linux-kernel On Sun, 2018-01-14 at 23:22 +0100, Dominik Brodowski wrote: > > + rcu_read_lock(); > ssid_ie = ieee80211_bss_get_ie(&wdev->current_bss->pub, > WLAN_EID_SSID); > if (!ssid_ie) > - break; nit-picking now: that "break" here may have been easier before these changes > + goto nla_rcu_unlock; > if (nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2)) > - goto nla_put_failure_locked; > + goto nla_put_failure_rcu_locked; > + nla_rcu_unlock: > + rcu_read_unlock(); > break; but after, perhaps it's easier to just do if (ssid_ie && nla_put(...) goto nla_put_failure_rcu_locked; and avoid the extra label (but yeah, it's getting late) johannes ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v3] nl80211: take RCU read lock when calling ieee80211_bss_get_ie() 2018-01-14 22:40 ` Johannes Berg @ 2018-01-15 7:12 ` Dominik Brodowski 2018-01-15 8:15 ` Johannes Berg 0 siblings, 1 reply; 6+ messages in thread From: Dominik Brodowski @ 2018-01-15 7:12 UTC (permalink / raw) To: Johannes Berg; +Cc: regressions, netdev, linux-wireless, linux-kernel As ieee80211_bss_get_ie() derefences an RCU to return ssid_ie, both the call to this function and any operation on this variable need protection by the RCU read lock. Fixes: 44905265bc15 ("nl80211: don't expose wdev->ssid for most interfaces") Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> --- > but after, perhaps it's easier to just do > > if (ssid_ie && > nla_put(...) > goto nla_put_failure_rcu_locked; > > and avoid the extra label (but yeah, it's getting late) OK, done that (and updated the commit message), and testet it. Thanks, Dominik diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index 2b3dbcd40e46..ed87a97fcb0b 100644 --- a/net/wireless/nl80211.c +++ b/net/wireless/nl80211.c @@ -2618,12 +2618,13 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag const u8 *ssid_ie; if (!wdev->current_bss) break; + rcu_read_lock(); ssid_ie = ieee80211_bss_get_ie(&wdev->current_bss->pub, WLAN_EID_SSID); - if (!ssid_ie) - break; - if (nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2)) - goto nla_put_failure_locked; + if (ssid_ie && + nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2)) + goto nla_put_failure_rcu_locked; + rcu_read_unlock(); break; } default: @@ -2635,6 +2636,8 @@ static int nl80211_send_iface(struct sk_buff *msg, u32 portid, u32 seq, int flag genlmsg_end(msg, hdr); return 0; + nla_put_failure_rcu_locked: + rcu_read_unlock(); nla_put_failure_locked: wdev_unlock(wdev); nla_put_failure: ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v3] nl80211: take RCU read lock when calling ieee80211_bss_get_ie() 2018-01-15 7:12 ` [PATCH v3] " Dominik Brodowski @ 2018-01-15 8:15 ` Johannes Berg 0 siblings, 0 replies; 6+ messages in thread From: Johannes Berg @ 2018-01-15 8:15 UTC (permalink / raw) To: Dominik Brodowski; +Cc: regressions, netdev, linux-wireless, linux-kernel On Mon, 2018-01-15 at 08:12 +0100, Dominik Brodowski wrote: > As ieee80211_bss_get_ie() derefences an RCU to return ssid_ie, both > the call to this function and any operation on this variable need > protection by the RCU read lock. > > Fixes: 44905265bc15 ("nl80211: don't expose wdev->ssid for most interfaces") > Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> > --- > > > but after, perhaps it's easier to just do > > > > if (ssid_ie && > > nla_put(...) > > goto nla_put_failure_rcu_locked; > > > > and avoid the extra label (but yeah, it's getting late) > > OK, done that (and updated the commit message), and testet it. > Applied, thanks! johannes ^ permalink raw reply [flat|nested] 6+ messages in thread
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2018-01-14 18:03 ` [PATCH] nl80211: take RCU read lock when calling ieee80211_bss_get_ie() Dominik Brodowski
2018-01-14 21:58 ` Johannes Berg
2018-01-14 22:22 ` [PATCH v2] " Dominik Brodowski
2018-01-14 22:40 ` Johannes Berg
2018-01-15 7:12 ` [PATCH v3] " Dominik Brodowski
2018-01-15 8:15 ` Johannes Berg
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