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The function arm_smmu_init_strtab_2lvl uses the expression
((1 << smmu->sid_bits) - 1)
to calculate the largest StreamID value. However, this fails for the
maximum allowed value of SMMU_IDR1.SIDSIZE which is 32. The C standard
states:
"If the value of the right operand is negative or is greater than or
equal to the width of the promoted left operand, the behavior is
undefined."
With smmu->sid_bits being 32, the prerequisites for undefined behavior
are met. We observed that the value of (1 << 32) is 1 and not 0 as we
initially expected.
Similar bit shift operations in arm_smmu_init_strtab_linear seem to not
be affected, because it appears to be unlikely for an SMMU to have
SMMU_IDR1.SIDSIZE set to 32 but then not support 2-level Stream tables
This issue was found by Ryan Huang <tzukui@google.com> on our team.
Fixes: ce410410f1 ("iommu/arm-smmu-v3: Add arm_smmu_strtab_l1/2_idx()")
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Link: https://lore.kernel.org/r/20241002015357.1766934-1-danielmentz@google.com
Signed-off-by: Will Deacon <will@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.