In the Linux kernel, the following vulnerability has been resolved:

vrf: Fix a potential NPD when removing a port from a VRF

RCU readers that identified a net device as a VRF port using
netif_is_l3_slave() assume that a subsequent call to
netdev_master_upper_dev_get_rcu() will return a VRF device. They then
continue to dereference its l3mdev operations.

This assumption is not always correct and can result in a NPD [1]. There
is no RCU synchronization when removing a port from a VRF, so it is
possible for an RCU reader to see a new master device (e.g., a bridge)
that does not have l3mdev operations.

Fix by adding RCU synchronization after clearing the IFF_L3MDEV_SLAVE
flag. Skip this synchronization when a net device is removed from a VRF
as part of its deletion and when the VRF device itself is deleted. In
the latter case an RCU grace period will pass by the time RTNL is
released.

[1]
BUG: kernel NULL pointer dereference, address: 0000000000000000
[...]
RIP: 0010:l3mdev_fib_table_rcu (net/l3mdev/l3mdev.c:181)
[...]
Call Trace:
<TASK>
l3mdev_fib_table_by_index (net/l3mdev/l3mdev.c:201 net/l3mdev/l3mdev.c:189)
__inet_bind (net/ipv4/af_inet.c:499 (discriminator 3))
inet_bind_sk (net/ipv4/af_inet.c:469)
__sys_bind (./include/linux/file.h:62 (discriminator 1) ./include/linux/file.h:83 (discriminator 1) net/socket.c:1951 (discriminator 1))
__x64_sys_bind (net/socket.c:1969 (discriminator 1) net/socket.c:1967 (discriminator 1) net/socket.c:1967 (discriminator 1))
do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

https://git.kernel.org/stable/c/2674d603a9e6970463b2b9ebcf8e31e90beae169

https://git.kernel.org/stable/c/2c022f582fd16a470df6ed9e7fb7e9fc48946d49

https://git.kernel.org/stable/c/3db8d078f7f652379ee394132b169d304f6eb4c1

https://git.kernel.org/stable/c/468defa0b70902a22f4478c1207624bc1b31c124

https://git.kernel.org/stable/c/4ab6fc60ed5a0344b60711b09bff1dc238d8d6a4

https://git.kernel.org/stable/c/8c2b792f04a3db97c9d8d2a45817e93f8884baf5

https://git.kernel.org/stable/c/a7a97f2303e63ede105c1d55ef53dc497364e11d

https://git.kernel.org/stable/c/d47204c127992da0c976ac9747070a575912e0fe

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