kernel/linux.git/net/bridge/br_fdb.c, branch linux-6.12.y

net: bridge: annotate data-races around fdb->{updated,used}

2026-01-23T10:18:37+00:00

[ Upstream commit b25a0b4a2193407aa72a4cd1df66a7ed07dd4f1e ] fdb->updated and fdb->used are read and written locklessly. Add READ_ONCE()/WRITE_ONCE() annotations. Fixes: 31cbc39b6344 ("net: bridge: add option to allow activity notifications for any fdb entries") Reported-by: syzbot+bfab43087ad57222ce96@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/695e3d74.050a0220.1c677c.035f.GAE@google.com/ Signed-off-by: Eric Dumazet Acked-by: Nikolay Aleksandrov Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260108093806.834459-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

move asm/unaligned.h to linux/unaligned.h

2024-10-02T21:23:23+00:00

asm/unaligned.h is always an include of asm-generic/unaligned.h; might as well move that thing to linux/unaligned.h and include that - there's nothing arch-specific in that header. auto-generated by the following: for i in `git grep -l -w asm/unaligned.h`; do sed -i -e "s/asm\/unaligned.h/linux\/unaligned.h/" $i done for i in `git grep -l -w asm-generic/unaligned.h`; do sed -i -e "s/asm-generic\/unaligned.h/linux\/unaligned.h/" $i done git mv include/asm-generic/unaligned.h include/linux/unaligned.h git mv tools/include/asm-generic/unaligned.h tools/include/linux/unaligned.h sed -i -e "/unaligned.h/d" include/asm-generic/Kbuild sed -i -e "s/__ASM_GENERIC/__LINUX/" include/linux/unaligned.h tools/include/linux/unaligned.h

net: bridge: br_fdb_external_learn_add(): always set EXT_LEARN

2024-09-04T23:36:21+00:00

When userspace wants to take over a fdb entry by setting it as EXTERN_LEARNED, we set both flags BR_FDB_ADDED_BY_EXT_LEARN and BR_FDB_ADDED_BY_USER in br_fdb_external_learn_add(). If the bridge updates the entry later because its port changed, we clear the BR_FDB_ADDED_BY_EXT_LEARN flag, but leave the BR_FDB_ADDED_BY_USER flag set. If userspace then wants to take over the entry again, br_fdb_external_learn_add() sees that BR_FDB_ADDED_BY_USER and skips setting the BR_FDB_ADDED_BY_EXT_LEARN flags, thus silently ignores the update. Fix this by always allowing to set BR_FDB_ADDED_BY_EXT_LEARN regardless if this was a user fdb entry or not. Fixes: 710ae7287737 ("net: bridge: Mark FDB entries that were added by user as such") Signed-off-by: Jonas Gorski Acked-by: Nikolay Aleksandrov Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20240903081958.29951-1-jonas.gorski@bisdn.de Signed-off-by: Jakub Kicinski

net: bridge: Use KMEM_CACHE instead of kmem_cache_create

2024-02-01T00:39:46+00:00

commit 0a31bd5f2bbb ("KMEM_CACHE(): simplify slab cache creation") introduces a new macro. Use the new KMEM_CACHE() macro instead of direct kmem_cache_create to simplify the creation of SLAB caches. Signed-off-by: Kunwu Chan Acked-by: Nikolay Aleksandrov Reviewed-by: Jiri Pirko Link: https://lore.kernel.org/r/20240130092536.73623-1-chentao@kylinos.cn Signed-off-by: Jakub Kicinski

net: bridge: Track and limit dynamically learned FDB entries

2023-10-18T00:39:01+00:00

A malicious actor behind one bridge port may spam the kernel with packets with a random source MAC address, each of which will create an FDB entry, each of which is a dynamic allocation in the kernel. There are roughly 2^48 different MAC addresses, further limited by the rhashtable they are stored in to 2^31. Each entry is of the type struct net_bridge_fdb_entry, which is currently 128 bytes big. This means the maximum amount of memory allocated for FDB entries is 2^31 * 128B = 256GiB, which is too much for most computers. Mitigate this by maintaining a per bridge count of those automatically generated entries in fdb_n_learned, and a limit in fdb_max_learned. If the limit is hit new entries are not learned anymore. For backwards compatibility the default setting of 0 disables the limit. User-added entries by netlink or from bridge or bridge port addresses are never blocked and do not count towards that limit. Introduce a new fdb entry flag BR_FDB_DYNAMIC_LEARNED to keep track of whether an FDB entry is included in the count. The flag is enabled for dynamically learned entries, and disabled for all other entries. This should be equivalent to BR_FDB_ADDED_BY_USER and BR_FDB_LOCAL being unset, but contrary to the two flags it can be toggled atomically. Atomicity is required here, as there are multiple callers that modify the flags, but are not under a common lock (br_fdb_update is the exception for br->hash_lock, br_fdb_external_learn_add for RTNL). Reviewed-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Signed-off-by: Johannes Nixdorf Link: https://lore.kernel.org/r/20231016-fdb_limit-v5-2-32cddff87758@avm.de Signed-off-by: Jakub Kicinski

net: bridge: Set BR_FDB_ADDED_BY_USER early in fdb_add_entry

2023-10-18T00:39:01+00:00

In preparation of the following fdb limit for dynamically learned entries, allow fdb_create to detect that the entry was added by the user. This way it can skip applying the limit in this case. Reviewed-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Signed-off-by: Johannes Nixdorf Link: https://lore.kernel.org/r/20231016-fdb_limit-v5-1-32cddff87758@avm.de Signed-off-by: Jakub Kicinski

net: Handle bulk delete policy in bridge driver

2023-10-13T09:00:30+00:00

The merge commit 92716869375b ("Merge branch 'br-flush-filtering'") added support for FDB flushing in bridge driver. The following patches will extend VXLAN driver to support FDB flushing as well. The netlink message for bulk delete is shared between the drivers. With the existing implementation, there is no way to prevent user from flushing with attributes that are not supported per driver. For example, when VNI will be added, user will not get an error for flush FDB entries in bridge with VNI, although this attribute is not relevant for bridge. As preparation for support of FDB flush in VXLAN driver, move the policy to be handled in bridge driver, later a new policy for VXLAN will be added in VXLAN driver. Do not pass 'vid' as part of ndo_fdb_del_bulk(), as this field is relevant only for bridge. Signed-off-by: Amit Cohen Reviewed-by: Ido Schimmel Signed-off-by: David S. Miller

bridge: switchdev: Allow device drivers to install locked FDB entries

2022-11-10T03:06:13+00:00

When the bridge is offloaded to hardware, FDB entries are learned and aged-out by the hardware. Some device drivers synchronize the hardware and software FDBs by generating switchdev events towards the bridge. When a port is locked, the hardware must not learn autonomously, as otherwise any host will blindly gain authorization. Instead, the hardware should generate events regarding hosts that are trying to gain authorization and their MAC addresses should be notified by the device driver as locked FDB entries towards the bridge driver. Allow device drivers to notify the bridge driver about such entries by extending the 'switchdev_notifier_fdb_info' structure with the 'locked' bit. The bit can only be set by device drivers and not by the bridge driver. Prevent a locked entry from being installed if MAB is not enabled on the bridge port. If an entry already exists in the bridge driver, reject the locked entry if the current entry does not have the "locked" flag set or if it points to a different port. The same semantics are implemented in the software data path. Signed-off-by: Hans J. Schultz Signed-off-by: Ido Schimmel Reviewed-by: Petr Machata Signed-off-by: Petr Machata Reviewed-by: Vladimir Oltean Acked-by: Nikolay Aleksandrov Signed-off-by: Jakub Kicinski

bridge: Add MAC Authentication Bypass (MAB) support

2022-11-04T03:46:32+00:00

Hosts that support 802.1X authentication are able to authenticate themselves by exchanging EAPOL frames with an authenticator (Ethernet bridge, in this case) and an authentication server. Access to the network is only granted by the authenticator to successfully authenticated hosts. The above is implemented in the bridge using the "locked" bridge port option. When enabled, link-local frames (e.g., EAPOL) can be locally received by the bridge, but all other frames are dropped unless the host is authenticated. That is, unless the user space control plane installed an FDB entry according to which the source address of the frame is located behind the locked ingress port. The entry can be dynamic, in which case learning needs to be enabled so that the entry will be refreshed by incoming traffic. There are deployments in which not all the devices connected to the authenticator (the bridge) support 802.1X. Such devices can include printers and cameras. One option to support such deployments is to unlock the bridge ports connecting these devices, but a slightly more secure option is to use MAB. When MAB is enabled, the MAC address of the connected device is used as the user name and password for the authentication. For MAB to work, the user space control plane needs to be notified about MAC addresses that are trying to gain access so that they will be compared against an allow list. This can be implemented via the regular learning process with the sole difference that learned FDB entries are installed with a new "locked" flag indicating that the entry cannot be used to authenticate the device. The flag cannot be set by user space, but user space can clear the flag by replacing the entry, thereby authenticating the device. Locked FDB entries implement the following semantics with regards to roaming, aging and forwarding: 1. Roaming: Locked FDB entries can roam to unlocked (authorized) ports, in which case the "locked" flag is cleared. FDB entries cannot roam to locked ports regardless of MAB being enabled or not. Therefore, locked FDB entries are only created if an FDB entry with the given {MAC, VID} does not already exist. This behavior prevents unauthenticated devices from disrupting traffic destined to already authenticated devices. 2. Aging: Locked FDB entries age and refresh by incoming traffic like regular entries. 3. Forwarding: Locked FDB entries forward traffic like regular entries. If user space detects an unauthorized MAC behind a locked port and wishes to prevent traffic with this MAC DA from reaching the host, it can do so using tc or a different mechanism. Enable the above behavior using a new bridge port option called "mab". It can only be enabled on a bridge port that is both locked and has learning enabled. Locked FDB entries are flushed from the port once MAB is disabled. A new option is added because there are pure 802.1X deployments that are not interested in notifications about locked FDB entries. Signed-off-by: Hans J. Schultz Signed-off-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Reviewed-by: Vladimir Oltean Signed-off-by: Jakub Kicinski

rtnetlink: add extack support in fdb del handlers

2022-05-09T10:58:20+00:00

Add extack support to .ndo_fdb_del in netdevice.h and all related methods. Signed-off-by: Alaa Mohamed Signed-off-by: David S. Miller