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

sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, as this is the only
member needed from the 'net' structure, but that would increase the size
of this fix, to use '*data' everywhere 'net->sctp.sctp_hmac_alg' is
used.

https://git.kernel.org/stable/c/3cd0659deb9c03535fd61839e91d4d4d3e51ac71

https://git.kernel.org/stable/c/ad673e514b2793b8d5902f6ba6ab7e890dea23d5

https://git.kernel.org/stable/c/ea62dd1383913b5999f3d16ae99d411f41b528d4

https://git.kernel.org/stable/c/f0bb3935470684306e4e04793a20ac4c4b08de0b