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Alexei Starovoitov
8d093b4e95
bpf programs sometimes do: bpf_cgrp_storage_get(&map, task->cgroups->dfl_cgrp, ...); It is safe to do, because cgroups->dfl_cgrp pointer is set diring init and never changes. The task->cgroups is also never NULL. It is also set during init and will change when task switches cgroups. For any trusted task pointer dereference of cgroups and dfl_cgrp should yield trusted pointers. The verifier wasn't aware of this. Hence in gcc compiled kernels task->cgroups dereference was producing PTR_TO_BTF_ID without modifiers while in clang compiled kernels the verifier recognizes __rcu tag in cgroups field and produces PTR_TO_BTF_ID | MEM_RCU | MAYBE_NULL. Tag cgroups and dfl_cgrp as trusted to equalize clang and gcc behavior. When GCC supports btf_type_tag such tagging will done directly in the type. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/bpf/20230303041446.3630-3-alexei.starovoitov@gmail.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.