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[ Upstream commit f620d66af3165838bfa845dcf9f5f9b4089bf508 ] Commit68d54ceeec("arm64: mte: Allow PTRACE_PEEKMTETAGS access to the zero page") attempted to fix ptrace() reading of tags from the zero page by marking it as PG_mte_tagged during cpu_enable_mte(). The same commit also changed the ptrace() tag access permission check to the VM_MTE vma flag while turning the page flag test into a WARN_ON_ONCE(). Attempting to set the PG_mte_tagged flag early with CONFIG_DEFERRED_STRUCT_PAGE_INIT enabled may either hang (after commitd77e59a8fc"arm64: mte: Lock a page for MTE tag initialisation") or have the flags cleared later during page_alloc_init_late(). In addition, pages_identical() -> memcmp_pages() will reject any comparison with the zero page as it is marked as tagged. Partially revert the above commit to avoid setting PG_mte_tagged on the zero page. Update the __access_remote_tags() warning on untagged pages to ignore the zero page since it is known to have the tags initialised. Note that all user mapping of the zero page are marked as pte_special(). The arm64 set_pte_at() will not call mte_sync_tags() on such pages, so PG_mte_tagged will remain cleared. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Fixes:68d54ceeec("arm64: mte: Allow PTRACE_PEEKMTETAGS access to the zero page") Reported-by: Gergely Kovacs <Gergely.Kovacs2@arm.com> Cc: stable@vger.kernel.org # 5.10.x Cc: Will Deacon <will@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: Lance Yang <lance.yang@linux.dev> Acked-by: Lance Yang <lance.yang@linux.dev> Reviewed-by: David Hildenbrand <david@redhat.com> Tested-by: Lance Yang <lance.yang@linux.dev> Signed-off-by: Will Deacon <will@kernel.org> [ Adjust context ] Signed-off-by: Sasha Levin <sashal@kernel.org> 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.