Song Liu ac9c05e0e4 bpf: Add kfunc bpf_get_file_xattr
It is common practice for security solutions to store tags/labels in
xattrs. To implement similar functionalities in BPF LSM, add new kfunc
bpf_get_file_xattr().

The first use case of bpf_get_file_xattr() is to implement file
verifications with asymmetric keys. Specificially, security applications
could use fsverity for file hashes and use xattr to store file signatures.
(kfunc for fsverity hash will be added in a separate commit.)

Currently, only xattrs with "user." prefix can be read with kfunc
bpf_get_file_xattr(). As use cases evolve, we may add a dedicated prefix
for bpf_get_file_xattr().

To avoid recursion, bpf_get_file_xattr can be only called from LSM hooks.

Signed-off-by: Song Liu <song@kernel.org>
Acked-by: Christian Brauner <brauner@kernel.org>
Acked-by: KP Singh <kpsingh@kernel.org>
Link: https://lore.kernel.org/r/20231129234417.856536-2-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-12-01 16:21:03 -08:00
2023-12-01 16:21:03 -08:00
2022-09-28 09:02:20 +02:00
2023-11-26 19:59:33 -08:00

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.
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