thr3ads.net - Linux Ethernet Bridging - [Bridge] [PATCH net 2/2] net: bridge: mcast: add and enforce startup query interval minimum [Dec 2021]

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Nikolay Aleksandrov

2021-Dec-27 17:21 UTC

[Bridge] [PATCH net 0/2] net: bridge: mcast: add and enforce query interval minimum

Hi,
This set adds and enforces 1 second minimum value for bridge multicast
query and startup query intervals in order to avoid rearming the timers
too often which could lock and crash the host. I doubt anyone is using
such low values or anything lower than 1 second, so it seems like a good
minimum. In order to be compatible if the value is lower then it is
overwritten and a log message is emitted, since we can't return an error
at this point.

Eric, I looked for the syzbot reports in its dashboard but couldn't find
them so I've added you as the reporter. If you point me to the reports
I can respin to give syzbot the credit.

I've prepared a global bridge igmp rate limiting patch but wasn't
sure if it's ok for -net. It adds a static limit of 32k packets per
second, I plan to send it for net-next with added drop counters for
each bridge so it can be easily debugged.

Original report can be seen at:
https://lore.kernel.org/netdev/e8b9ce41-57b9-b6e2-a46a-ff9c791cf0ba at
gmail.com/

Thanks,
 Nik

Nikolay Aleksandrov (2):
  net: bridge: mcast: add and enforce query interval minimum
  net: bridge: mcast: add and enforce startup query interval minimum

 net/bridge/br_multicast.c    | 32 ++++++++++++++++++++++++++++++++
 net/bridge/br_netlink.c      |  4 ++--
 net/bridge/br_private.h      |  6 ++++++
 net/bridge/br_sysfs_br.c     |  4 ++--
 net/bridge/br_vlan_options.c |  4 ++--
 5 files changed, 44 insertions(+), 6 deletions(-)

-- 
2.33.1

Nikolay Aleksandrov

2021-Dec-27 17:21 UTC

head link

[Bridge] [PATCH net 1/2] net: bridge: mcast: add and enforce query interval minimum

As reported[1] if query interval is set too low and we have multiple
bridges or even a single bridge with multiple querier vlans configured
we can crash the machine. Add a 1 second minimum which must be enforced
by overwriting the value if set lower (i.e. without returning an error) to
avoid breaking user-space. If that happens a log message is emitted to let
the administrator know that the interval has been set to the minimum.
The issue has been present since these intervals could be user-controlled.

[1] https://lore.kernel.org/netdev/e8b9ce41-57b9-b6e2-a46a-ff9c791cf0ba at
gmail.com/

Fixes: d902eee43f19 ("bridge: Add multicast count/interval sysfs
entries")
Reported-by: Eric Dumazet <eric.dumazet at gmail.com>
Signed-off-by: Nikolay Aleksandrov <nikolay at nvidia.com>
---
 net/bridge/br_multicast.c    | 16 ++++++++++++++++
 net/bridge/br_netlink.c      |  2 +-
 net/bridge/br_private.h      |  3 +++
 net/bridge/br_sysfs_br.c     |  2 +-
 net/bridge/br_vlan_options.c |  2 +-
 5 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index f3d751105343..998da4a2d209 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -4522,6 +4522,22 @@ int br_multicast_set_mld_version(struct net_bridge_mcast
*brmctx,
 }
 #endif
 
+void br_multicast_set_query_intvl(struct net_bridge_mcast *brmctx,
+				  unsigned long val)
+{
+	unsigned long intvl_jiffies = clock_t_to_jiffies(val);
+
+	if (intvl_jiffies < BR_MULTICAST_QUERY_INTVL_MIN) {
+		br_info(brmctx->br,
+			"trying to set multicast query interval below minimum, setting to %lu
(%ums)\n",
+			jiffies_to_clock_t(BR_MULTICAST_QUERY_INTVL_MIN),
+			jiffies_to_msecs(BR_MULTICAST_QUERY_INTVL_MIN));
+		intvl_jiffies = BR_MULTICAST_QUERY_INTVL_MIN;
+	}
+
+	brmctx->multicast_query_interval = intvl_jiffies;
+}
+
 /**
  * br_multicast_list_adjacent - Returns snooped multicast addresses
  * @dev:	The bridge port adjacent to which to retrieve addresses
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 0c8b5f1a15bc..701dd8b8455e 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -1357,7 +1357,7 @@ static int br_changelink(struct net_device *brdev, struct
nlattr *tb[],
 	if (data[IFLA_BR_MCAST_QUERY_INTVL]) {
 		u64 val = nla_get_u64(data[IFLA_BR_MCAST_QUERY_INTVL]);
 
-		br->multicast_ctx.multicast_query_interval = clock_t_to_jiffies(val);
+		br_multicast_set_query_intvl(&br->multicast_ctx, val);
 	}
 
 	if (data[IFLA_BR_MCAST_QUERY_RESPONSE_INTVL]) {
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index c0efd697865a..4ed7f11042e8 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -28,6 +28,7 @@
 #define BR_MAX_PORTS	(1<<BR_PORT_BITS)
 
 #define BR_MULTICAST_DEFAULT_HASH_MAX 4096
+#define BR_MULTICAST_QUERY_INTVL_MIN msecs_to_jiffies(1000)
 
 #define BR_HWDOM_MAX BITS_PER_LONG
 
@@ -963,6 +964,8 @@ int br_multicast_dump_querier_state(struct sk_buff *skb,
 				    int nest_attr);
 size_t br_multicast_querier_state_size(void);
 size_t br_rports_size(const struct net_bridge_mcast *brmctx);
+void br_multicast_set_query_intvl(struct net_bridge_mcast *brmctx,
+				  unsigned long val);
 
 static inline bool br_group_is_l2(const struct br_ip *group)
 {
diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index d9a89ddd0331..f5bd1114a434 100644
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -658,7 +658,7 @@ static ssize_t multicast_query_interval_show(struct device
*d,
 static int set_query_interval(struct net_bridge *br, unsigned long val,
 			      struct netlink_ext_ack *extack)
 {
-	br->multicast_ctx.multicast_query_interval = clock_t_to_jiffies(val);
+	br_multicast_set_query_intvl(&br->multicast_ctx, val);
 	return 0;
 }
 
diff --git a/net/bridge/br_vlan_options.c b/net/bridge/br_vlan_options.c
index 8ffd4ed2563c..bf1ac0874279 100644
--- a/net/bridge/br_vlan_options.c
+++ b/net/bridge/br_vlan_options.c
@@ -521,7 +521,7 @@ static int br_vlan_process_global_one_opts(const struct
net_bridge *br,
 		u64 val;
 
 		val = nla_get_u64(tb[BRIDGE_VLANDB_GOPTS_MCAST_QUERY_INTVL]);
-		v->br_mcast_ctx.multicast_query_interval = clock_t_to_jiffies(val);
+		br_multicast_set_query_intvl(&v->br_mcast_ctx, val);
 		*changed = true;
 	}
 	if (tb[BRIDGE_VLANDB_GOPTS_MCAST_QUERY_RESPONSE_INTVL]) {
-- 
2.33.1

Nikolay Aleksandrov

2021-Dec-27 17:21 UTC

head link

[Bridge] [PATCH net 2/2] net: bridge: mcast: add and enforce startup query interval minimum

As reported[1] if startup query interval is set too low in combination with
large number of startup queries and we have multiple bridges or even a
single bridge with multiple querier vlans configured we can crash the
machine. Add a 1 second minimum which must be enforced by overwriting the
value if set lower (i.e. without returning an error) to avoid breaking
user-space. If that happens a log message is emitted to let the admin know
that the startup interval has been set to the minimum. It doesn't make
sense to make the startup interval lower than the normal query interval
so use the same value of 1 second. The issue has been present since these
intervals could be user-controlled.

[1] https://lore.kernel.org/netdev/e8b9ce41-57b9-b6e2-a46a-ff9c791cf0ba at
gmail.com/

Fixes: d902eee43f19 ("bridge: Add multicast count/interval sysfs
entries")
Reported-by: Eric Dumazet <eric.dumazet at gmail.com>
Signed-off-by: Nikolay Aleksandrov <nikolay at nvidia.com>
---
 net/bridge/br_multicast.c    | 16 ++++++++++++++++
 net/bridge/br_netlink.c      |  2 +-
 net/bridge/br_private.h      |  3 +++
 net/bridge/br_sysfs_br.c     |  2 +-
 net/bridge/br_vlan_options.c |  2 +-
 5 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 998da4a2d209..de2409889489 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -4538,6 +4538,22 @@ void br_multicast_set_query_intvl(struct net_bridge_mcast
*brmctx,
 	brmctx->multicast_query_interval = intvl_jiffies;
 }
 
+void br_multicast_set_startup_query_intvl(struct net_bridge_mcast *brmctx,
+					  unsigned long val)
+{
+	unsigned long intvl_jiffies = clock_t_to_jiffies(val);
+
+	if (intvl_jiffies < BR_MULTICAST_STARTUP_QUERY_INTVL_MIN) {
+		br_info(brmctx->br,
+			"trying to set multicast startup query interval below minimum, setting
to %lu (%ums)\n",
+			jiffies_to_clock_t(BR_MULTICAST_STARTUP_QUERY_INTVL_MIN),
+			jiffies_to_msecs(BR_MULTICAST_STARTUP_QUERY_INTVL_MIN));
+		intvl_jiffies = BR_MULTICAST_STARTUP_QUERY_INTVL_MIN;
+	}
+
+	brmctx->multicast_startup_query_interval = intvl_jiffies;
+}
+
 /**
  * br_multicast_list_adjacent - Returns snooped multicast addresses
  * @dev:	The bridge port adjacent to which to retrieve addresses
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 701dd8b8455e..2ff83d84230d 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -1369,7 +1369,7 @@ static int br_changelink(struct net_device *brdev, struct
nlattr *tb[],
 	if (data[IFLA_BR_MCAST_STARTUP_QUERY_INTVL]) {
 		u64 val = nla_get_u64(data[IFLA_BR_MCAST_STARTUP_QUERY_INTVL]);
 
-		br->multicast_ctx.multicast_startup_query_interval =
clock_t_to_jiffies(val);
+		br_multicast_set_startup_query_intvl(&br->multicast_ctx, val);
 	}
 
 	if (data[IFLA_BR_MCAST_STATS_ENABLED]) {
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 4ed7f11042e8..2187a0c3fd22 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -29,6 +29,7 @@
 
 #define BR_MULTICAST_DEFAULT_HASH_MAX 4096
 #define BR_MULTICAST_QUERY_INTVL_MIN msecs_to_jiffies(1000)
+#define BR_MULTICAST_STARTUP_QUERY_INTVL_MIN BR_MULTICAST_QUERY_INTVL_MIN
 
 #define BR_HWDOM_MAX BITS_PER_LONG
 
@@ -966,6 +967,8 @@ size_t br_multicast_querier_state_size(void);
 size_t br_rports_size(const struct net_bridge_mcast *brmctx);
 void br_multicast_set_query_intvl(struct net_bridge_mcast *brmctx,
 				  unsigned long val);
+void br_multicast_set_startup_query_intvl(struct net_bridge_mcast *brmctx,
+					  unsigned long val);
 
 static inline bool br_group_is_l2(const struct br_ip *group)
 {
diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index f5bd1114a434..7b0c19772111 100644
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -706,7 +706,7 @@ static ssize_t multicast_startup_query_interval_show(
 static int set_startup_query_interval(struct net_bridge *br, unsigned long val,
 				      struct netlink_ext_ack *extack)
 {
-	br->multicast_ctx.multicast_startup_query_interval =
clock_t_to_jiffies(val);
+	br_multicast_set_startup_query_intvl(&br->multicast_ctx, val);
 	return 0;
 }
 
diff --git a/net/bridge/br_vlan_options.c b/net/bridge/br_vlan_options.c
index bf1ac0874279..a6382973b3e7 100644
--- a/net/bridge/br_vlan_options.c
+++ b/net/bridge/br_vlan_options.c
@@ -535,7 +535,7 @@ static int br_vlan_process_global_one_opts(const struct
net_bridge *br,
 		u64 val;
 
 		val = nla_get_u64(tb[BRIDGE_VLANDB_GOPTS_MCAST_STARTUP_QUERY_INTVL]);
-		v->br_mcast_ctx.multicast_startup_query_interval =
clock_t_to_jiffies(val);
+		br_multicast_set_startup_query_intvl(&v->br_mcast_ctx, val);
 		*changed = true;
 	}
 	if (tb[BRIDGE_VLANDB_GOPTS_MCAST_QUERIER]) {
-- 
2.33.1

patchwork-bot+netdevbpf at kernel.org

2021-Dec-29 22:20 UTC

head link

[Bridge] [PATCH net 0/2] net: bridge: mcast: add and enforce query interval minimum

Hello:

This series was applied to netdev/net.git (master)
by Jakub Kicinski <kuba at kernel.org>:

On Mon, 27 Dec 2021 19:21:14 +0200 you wrote:> Hi,
> This set adds and enforces 1 second minimum value for bridge multicast
> query and startup query intervals in order to avoid rearming the timers
> too often which could lock and crash the host. I doubt anyone is using
> such low values or anything lower than 1 second, so it seems like a good
> minimum. In order to be compatible if the value is lower then it is
> overwritten and a log message is emitted, since we can't return an
error
> at this point.
> 
> [...]
Here is the summary with links:
  - [net,1/2] net: bridge: mcast: add and enforce query interval minimum
    https://git.kernel.org/netdev/net/c/99b40610956a
  - [net,2/2] net: bridge: mcast: add and enforce startup query interval minimum
    https://git.kernel.org/netdev/net/c/f83a112bd91a

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Linux Ethernet Bridging - Dec 2021 - [Bridge] [PATCH net 2/2] net: bridge: mcast: add and enforce startup query interval minimum

[Bridge] [PATCH net 0/2] net: bridge: mcast: add and enforce query interval minimum

[Bridge] [PATCH net 1/2] net: bridge: mcast: add and enforce query interval minimum

[Bridge] [PATCH net 2/2] net: bridge: mcast: add and enforce startup query interval minimum

[Bridge] [PATCH net 0/2] net: bridge: mcast: add and enforce query interval minimum