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Mark Rutland 4105dd76bc arm64: ptrace: fix partial SETREGSET for NT_ARM_POE commit `594bfc4947` upstream. Currently poe_set() doesn't initialize the temporary 'ctrl' variable, and a SETREGSET call with a length of zero will leave this uninitialized. Consequently an arbitrary value will be written back to target->thread.por_el0, potentially leaking up to 64 bits of memory from the kernel stack. The read is limited to a specific slot on the stack, and the issue does not provide a write mechanism. Fix this by initializing the temporary value before copying the regset from userspace, as for other regsets (e.g. NT_PRSTATUS, NT_PRFPREG, NT_ARM_SYSTEM_CALL). In the case of a zero-length write, the existing contents of POR_EL1 will be retained. Before this patch: \| # ./poe-test \| Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d \| SETREGSET(nt=0x40f, len=8) wrote 8 bytes \| \| Attempting to read NT_ARM_POE::por_el0 \| GETREGSET(nt=0x40f, len=8) read 8 bytes \| Read NT_ARM_POE::por_el0 = 0x900d900d900d900d \| \| Attempting to write NT_ARM_POE (zero length) \| SETREGSET(nt=0x40f, len=0) wrote 0 bytes \| \| Attempting to read NT_ARM_POE::por_el0 \| GETREGSET(nt=0x40f, len=8) read 8 bytes \| Read NT_ARM_POE::por_el0 = 0xffff8000839c3d50 After this patch: \| # ./poe-test \| Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d \| SETREGSET(nt=0x40f, len=8) wrote 8 bytes \| \| Attempting to read NT_ARM_POE::por_el0 \| GETREGSET(nt=0x40f, len=8) read 8 bytes \| Read NT_ARM_POE::por_el0 = 0x900d900d900d900d \| \| Attempting to write NT_ARM_POE (zero length) \| SETREGSET(nt=0x40f, len=0) wrote 0 bytes \| \| Attempting to read NT_ARM_POE::por_el0 \| GETREGSET(nt=0x40f, len=8) read 8 bytes \| Read NT_ARM_POE::por_el0 = 0x900d900d900d900d Fixes: `1751981992` ("arm64/ptrace: add support for FEAT_POE") Cc: <stable@vger.kernel.org> # 6.12.x Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Joey Gouly <joey.gouly@arm.com> Cc: Will Deacon <will@kernel.org> Reviewed-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20241205121655.1824269-4-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2024-12-14 20:03:22 +01:00
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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 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.