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6fdd5d2f8c
64-bit RISC-V kernels have the kernel image mapped separately to alias
the linear map. The linear map and the kernel image map are documented
as "direct mapping" and "kernel" respectively in [1].
At image load time, the linear map corresponding to the kernel image
is set to PAGE_READ permission, and the kernel image map is set to
PAGE_READ|PAGE_EXEC.
When the initmem is freed, the pages in the linear map should be
restored to PAGE_READ|PAGE_WRITE, whereas the corresponding pages in
the kernel image map should be restored to PAGE_READ, by removing the
PAGE_EXEC permission.
This is not the case. For 64-bit kernels, only the linear map is
restored to its proper page permissions at initmem free, and not the
kernel image map.
In practise this results in that the kernel can potentially jump to
dead __init code, and start executing invalid instructions, without
getting an exception.
Restore the freed initmem properly, by setting both the kernel image
map to the correct permissions.
[1] Documentation/riscv/vm-layout.rst
Fixes:
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.