• Dan Williams's avatar
    nfit, libnvdimm: fix interleave set cookie calculation · 86ef58a4
    Dan Williams authored
    The interleave-set cookie is a sum that sanity checks the composition of
    an interleave set has not changed from when the namespace was initially
    created.  The checksum is calculated by sorting the DIMMs by their
    location in the interleave-set. The comparison for the sort must be
    64-bit wide, not byte-by-byte as performed by memcmp() in the broken
    case.
    
    Fix the implementation to accept correct cookie values in addition to
    the Linux "memcmp" order cookies, but only allow correct cookies to be
    generated going forward. It does mean that namespaces created by
    third-party-tooling, or created by newer kernels with this fix, will not
    validate on older kernels. However, there are a couple mitigating
    conditions:
    
        1/ platforms with namespace-label capable NVDIMMs are not widely
           available.
    
        2/ interleave-sets with a single-dimm are by definition not affected
           (nothing to sort). This covers the QEMU-KVM NVDIMM emulation case.
    
    The cookie stored in the namespace label will be fixed by any write the
    namespace label, the most straightforward way to achieve this is to
    write to the "alt_name" attribute of a namespace in sysfs.
    
    Cc: <stable@vger.kernel.org>
    Fixes: eaf96153 ("libnvdimm, nfit: add interleave-set state-tracking infrastructure")
    Reported-by: default avatarNicholas Moulin <nicholas.w.moulin@linux.intel.com>
    Tested-by: default avatarNicholas Moulin <nicholas.w.moulin@linux.intel.com>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    86ef58a4
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