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Jakub Sitnicki says:
====================
net/tls: Annotate lockless access to sk_prot
We have recently noticed that there is a case of lockless read/write to
sk->sk_prot [0]. sockmap code on psock tear-down writes to sk->sk_prot,
while holding sk_callback_lock. Concurrently, tcp can access it. Usually to
read out the sk_prot pointer and invoke one of the ops,
sk->sk_prot->handler().
The lockless write (lockless in regard to concurrent reads) happens on the
following paths:
tcp_bpf_{recvmsg|sendmsg} / sock_map_unref
sk_psock_put
sk_psock_drop
sk_psock_restore_proto
WRITE_ONCE(sk->sk_prot, proto)
To prevent load/store tearing [1], and to make tooling aware of intentional
shared access [2], we need to annotate sites that access sk_prot with
READ_ONCE/WRITE_ONCE.
This series kicks off the effort to do it. Starting with net/tls.
[0] https://lore.kernel.org/bpf/a6bf279e-a998-84ab-4371-cd6c1ccbca5d@gmail.com/
[1] https://lwn.net/Articles/793253/
[2] https://github.com/google/ktsan/wiki/READ_ONCE-and-WRITE_ONCE
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.