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When attaching a flow dissector program to a network namespace with
bpf(BPF_PROG_ATTACH, ...) we grab a reference to bpf_prog.
If netns gets destroyed while a flow dissector is still attached, and there
are no other references to the prog, we leak the reference and the program
remains loaded.
Leak can be reproduced by running flow dissector tests from selftests/bpf:
# bpftool prog list
# ./test_flow_dissector.sh
...
selftests: test_flow_dissector [PASS]
# bpftool prog list
4: flow_dissector name _dissect tag e314084d332a5338 gpl
loaded_at 2020-05-20T18:50:53+0200 uid 0
xlated 552B jited 355B memlock 4096B map_ids 3,4
btf_id 4
#
Fix it by detaching the flow dissector program when netns is going away.
Fixes: d58e468b11 ("flow_dissector: implements flow dissector BPF hook")
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20200521083435.560256-1-jakub@cloudflare.com
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.