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host_stage2_adjust_range() tries to find the largest block mapping that
fits within a memory or mmio region (represented by a kvm_mem_range in
this function) during host stage-2 faults under pKVM. To do so, it walks
the host stage-2 page-table, finds the faulting PTE and its level, and
then progressively increments the level until it finds a granule of the
appropriate size. However, the condition in the loop implementing the
above is broken as it checks kvm_level_supports_block_mapping() for the
next level instead of the current, so pKVM may attempt to map a region
larger than can be covered with a single block.
This is not a security problem and is quite rare in practice (the
kvm_mem_range check usually forces host_stage2_adjust_range() to choose a
smaller granule), but this is clearly not the expected behaviour.
Refactor the loop to fix the bug and improve readability.
Fixes: c4f0935e4d ("KVM: arm64: Optimize host memory aborts")
Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20250625105548.984572-1-qperret@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
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.