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When there is bpf_list_head or bpf_rb_root field in map value, the free of map btf and the free of map value may run concurrently and there may be use-after-free problem, so add two test cases to demonstrate it. And the use-after-free problem can been easily reproduced by using bpf_next tree and a KASAN-enabled kernel. The first test case tests the racing between the free of map btf and the free of array map. It constructs the racing by releasing the array map in the end after other ref-counter of map btf has been released. To delay the free of array map and make it be invoked after btf_free_rcu() is invoked, it stresses system_unbound_wq by closing multiple percpu array maps before it closes the array map. The second case tests the racing between the free of map btf and the free of inner map. Beside using the similar method as the first one does, it uses bpf_map_delete_elem() to delete the inner map and to defer the release of inner map after one RCU grace period. The reason for using two skeletons is to prevent the release of outer map and inner map in map_in_map_btf.c interfering the release of bpf map in normal_map_btf.c. Signed-off-by: Hou Tao <houtao1@huawei.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/bpf/20231216035510.4030605-1-houtao@huaweicloud.com |
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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.