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commit68d54ceeecupstream. The ptrace(PTRACE_PEEKMTETAGS) implementation checks whether the user page has valid tags (mapped with PROT_MTE) by testing the PG_mte_tagged page flag. If this bit is cleared, ptrace(PTRACE_PEEKMTETAGS) returns -EIO. A newly created (PROT_MTE) mapping points to the zero page which had its tags zeroed during cpu_enable_mte(). If there were no prior writes to this mapping, ptrace(PTRACE_PEEKMTETAGS) fails with -EIO since the zero page does not have the PG_mte_tagged flag set. Set PG_mte_tagged on the zero page when its tags are cleared during boot. In addition, to avoid ptrace(PTRACE_PEEKMTETAGS) succeeding on !PROT_MTE mappings pointing to the zero page, change the __access_remote_tags() check to (vm_flags & VM_MTE) instead of PG_mte_tagged. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Fixes:34bfeea4a9("arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE") Cc: <stable@vger.kernel.org> # 5.10.x Cc: Will Deacon <will@kernel.org> Reported-by: Luis Machado <luis.machado@linaro.org> Tested-by: Luis Machado <luis.machado@linaro.org> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Link: https://lore.kernel.org/r/20210210180316.23654-1-catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 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.