In the Linux kernel, the following vulnerability has been resolved:
nexthop: Fix memory leaks in nexthop notification chain listeners
syzkaller discovered memory leaks [1] that can be reduced to the following commands:
# ip nexthop add id 1 blackhole # devlink dev reload pci/0000:06:00.0
As part of the reload flow, mlxsw will unregister its netdevs and then unregister from the nexthop notification chain. Before unregistering from the notification chain, mlxsw will receive delete notifications for nexthop objects using netdevs registered by mlxsw or their uppers. mlxsw will not receive notifications for nexthops using netdevs that are not dismantled as part of the reload flow. For example, the blackhole nexthop above that internally uses the loopback netdev as its nexthop device.
One way to fix this problem is to have listeners flush their nexthop tables after unregistering from the notification chain. This is error-prone as evident by this patch and also not symmetric with the registration path where a listener receives a dump of all the existing nexthops.
Therefore, fix this problem by replaying delete notifications for the listener being unregistered. This is symmetric to the registration path and also consistent with the netdev notification chain.
The above means that unregister_nexthop_notifier(), like register_nexthop_notifier(), will have to take RTNL in order to iterate over the existing nexthops and that any callers of the function cannot hold RTNL. This is true for mlxsw and netdevsim, but not for the VXLAN driver. To avoid a deadlock, change the latter to unregister its nexthop listener without holding RTNL, making it symmetric to the registration path.
[1] unreferenced object 0xffff88806173d600 (size 512): comm "syz-executor.0", pid 1290, jiffies 4295583142 (age 143.507s) hex dump (first 32 bytes): 41 9d 1e 60 80 88 ff ff 08 d6 73 61 80 88 ff ff A..`......sa.... 08 d6 73 61 80 88 ff ff 01 00 00 00 00 00 00 00 ..sa............ backtrace: [<ffffffff81a6b576>] kmemleak_alloc_recursive include/linux/kmemleak.h:43 [inline] [<ffffffff81a6b576>] slab_post_alloc_hook+0x96/0x490 mm/slab.h:522 [<ffffffff81a716d3>] slab_alloc_node mm/slub.c:3206 [inline] [<ffffffff81a716d3>] slab_alloc mm/slub.c:3214 [inline] [<ffffffff81a716d3>] kmem_cache_alloc_trace+0x163/0x370 mm/slub.c:3231 [<ffffffff82e8681a>] kmalloc include/linux/slab.h:591 [inline] [<ffffffff82e8681a>] kzalloc include/linux/slab.h:721 [inline] [<ffffffff82e8681a>] mlxsw_sp_nexthop_obj_group_create drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:4918 [inline] [<ffffffff82e8681a>] mlxsw_sp_nexthop_obj_new drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:5054 [inline] [<ffffffff82e8681a>] mlxsw_sp_nexthop_obj_event+0x59a/0x2910 drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:5239 [<ffffffff813ef67d>] notifier_call_chain+0xbd/0x210 kernel/notifier.c:83 [<ffffffff813f0662>] blocking_notifier_call_chain kernel/notifier.c:318 [inline] [<ffffffff813f0662>] blocking_notifier_call_chain+0x72/0xa0 kernel/notifier.c:306 [<ffffffff8384b9c6>] call_nexthop_notifiers+0x156/0x310 net/ipv4/nexthop.c:244 [<ffffffff83852bd8>] insert_nexthop net/ipv4/nexthop.c:2336 [inline] [<ffffffff83852bd8>] nexthop_add net/ipv4/nexthop.c:2644 [inline] [<ffffffff83852bd8>] rtm_new_nexthop+0x14e8/0x4d10 net/ipv4/nexthop.c:2913 [<ffffffff833e9a78>] rtnetlink_rcv_msg+0x448/0xbf0 net/core/rtnetlink.c:5572 [<ffffffff83608703>] netlink_rcv_skb+0x173/0x480 net/netlink/af_netlink.c:2504 [<ffffffff833de032>] rtnetlink_rcv+0x22/0x30 net/core/rtnetlink.c:5590 [<ffffffff836069de>] netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] [<ffffffff836069de>] netlink_unicast+0x5ae/0x7f0 net/netlink/af_netlink.c:1340 [<ffffffff83607501>] netlink_sendmsg+0x8e1/0xe30 net/netlink/af_netlink.c:1929 [<ffffffff832fde84>] sock_sendmsg_nosec net/socket.c:704 [inline ---truncated---
CVSS Details
- CVSS 3.1 Base Score: 7.1
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Debian | — | Upgrade linux | Jul 30, 2024 | May 21, 2024 |
| Redhat_linux | — | No solution exists | Jul 9, 2025 | May 21, 2024 |
| Suse | — | Upgrade kernel-devel-azureUpgrade ocfs2-kmp-rtUpgrade dtb-rockchipUpgrade kernel-default-base-rebuildUpgrade kernel-default-vdsoUpgrade kernel-64kb-livepatch-develUpgrade kernel-obs-buildUpgrade dtb-caviumUpgrade kernel-devel-rtUpgrade kernel-kvmsmallUpgrade ocfs2-kmp-defaultUpgrade dtb-allwinnerUpgrade kernel-rt-livepatchUpgrade kernel-source-azureUpgrade kernel-azure-livepatch-develUpgrade kernel-64kb-develUpgrade kernel-rt_debug-develUpgrade kernel-rt-develUpgrade gfs2-kmp-azureUpgrade kselftests-kmp-azureUpgrade kernel-kvmsmall-develUpgrade ocfs2-kmp-azureUpgrade kernel-64kbUpgrade gfs2-kmp-rtUpgrade kernel-azureUpgrade dtb-xilinxUpgrade reiserfs-kmp-azureUpgrade kselftests-kmp-64kbUpgrade gfs2-kmp-64kbUpgrade kernel-rtUpgrade kernel-rt-extraUpgrade kernel-debug-vdsoUpgrade dtb-amazonUpgrade kernel-zfcpdumpUpgrade gfs2-kmp-defaultUpgrade dtb-exynosUpgrade kernel-default-optionalUpgrade cluster-md-kmp-rtUpgrade dtb-qcomUpgrade dtb-mediatekUpgrade dlm-kmp-64kbUpgrade cluster-md-kmp-azureUpgrade dtb-armUpgrade kernel-azure-develUpgrade dtb-alteraUpgrade kernel-symsUpgrade kernel-azure-optionalUpgrade kernel-develUpgrade kernel-sourceUpgrade kernel-source-vanillaUpgrade kernel-default-develUpgrade dtb-lgUpgrade kernel-syms-azureUpgrade reiserfs-kmp-rtUpgrade kernel-azure-extraUpgrade kernel-rt_debug-livepatch-develUpgrade dtb-marvellUpgrade kernel-docsUpgrade dtb-amdUpgrade kernel-debug-develUpgrade dlm-kmp-azureUpgrade kernel-rt_debugUpgrade kernel-obs-qaUpgrade dtb-hisiliconUpgrade cluster-md-kmp-64kbUpgrade kernel-default-extraUpgrade kernel-syms-rtUpgrade kernel-rt_debug-vdsoUpgrade kernel-kvmsmall-livepatch-develUpgrade kernel-rt-optionalUpgrade dtb-amlogicUpgrade kernel-64kb-extraUpgrade kernel-default-livepatchUpgrade dtb-renesasUpgrade kernel-64kb-optionalUpgrade dlm-kmp-rtUpgrade dtb-nvidiaUpgrade kernel-macrosUpgrade kernel-debug-livepatch-develUpgrade kernel-rt-livepatch-develUpgrade kernel-docs-htmlUpgrade kernel-kvmsmall-vdsoUpgrade dtb-broadcomUpgrade kernel-default-baseUpgrade dtb-socionextUpgrade dtb-sprdUpgrade kernel-azure-vdsoUpgrade kselftests-kmp-defaultUpgrade kselftests-kmp-rtUpgrade cluster-md-kmp-defaultUpgrade reiserfs-kmp-defaultUpgrade dtb-freescaleUpgrade dlm-kmp-defaultUpgrade kernel-debugUpgrade reiserfs-kmp-64kbUpgrade dtb-appleUpgrade kernel-rt-vdsoUpgrade kernel-source-rtUpgrade ocfs2-kmp-64kbUpgrade dtb-apmUpgrade kernel-defaultUpgrade kernel-default-livepatch-devel | Aug 9, 2024 | May 21, 2024 |
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