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Classic BPF programs have been identified as potential vectors for intra-mode Branch Target Injection (BTI) attacks. Classic BPF programs can be run by unprivileged users. They allow unprivileged code to execute inside the kernel. Attackers can use unprivileged cBPF to craft branch history in kernel mode that can influence the target of indirect branches. Introduce a branch history buffer (BHB) clearing sequence during the JIT compilation of classic BPF programs. The clearing sequence is the same as is used in previous mitigations to protect syscalls. Since eBPF programs already have their own mitigations in place, only insert the call on classic programs that aren't run by privileged users. Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.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 reStructuredText 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.