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commit074a1e1167upstream. The virt_addr_valid() function is meant to return true iff virt_to_page() will return a valid struct page reference. This is true iff the address provided is found within the unmapped address range between PAGE_OFFSET & MAP_BASE, but we don't currently check for that condition. Instead we simply mask the address to obtain what will be a physical address if the virtual address is indeed in the desired range, shift it to form a PFN & then call pfn_valid(). This can incorrectly return true if called with a virtual address which, after masking, happens to form a physical address corresponding to a valid PFN. For example we may vmalloc an address in the kernel mapped region starting a MAP_BASE & obtain the virtual address: addr = 0xc000000000002000 When masked by virt_to_phys(), which uses __pa() & in turn CPHYSADDR(), we obtain the following (bogus) physical address: addr = 0x2000 In a common system with PHYS_OFFSET=0 this will correspond to a valid struct page which should really be accessed by virtual address PAGE_OFFSET+0x2000, causing virt_addr_valid() to incorrectly return 1 indicating that the original address corresponds to a struct page. This is equivalent to the ARM64 change made in commitca219452c6("arm64: Correctly bounds check virt_addr_valid"). This fixes fallout when hardened usercopy is enabled caused by the related commit517e1fbeb6("mm/usercopy: Drop extra is_vmalloc_or_module() check") which removed a check for the vmalloc range that was present from the introduction of the hardened usercopy feature. Signed-off-by: Paul Burton <paul.burton@mips.com> References:ca219452c6("arm64: Correctly bounds check virt_addr_valid") References:517e1fbeb6("mm/usercopy: Drop extra is_vmalloc_or_module() check") Reported-by: Julien Cristau <jcristau@debian.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Tested-by: YunQiang Su <ysu@wavecomp.com> URL: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=929366 Cc: stable@vger.kernel.org # v4.12+ Cc: linux-mips@vger.kernel.org Cc: Yunqiang Su <ysu@wavecomp.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.