OpenAFS Master Repository branch, master, updated. BP-openafs-stable-1_8_x-98-g54e84a9

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit 54e84a98f9747bb5bb2ad4b8031115ad7684c914
Author: Benjamin Kaduk <kaduk@mit.edu>
Date:   Fri Apr 13 08:07:59 2018 -0500

    BSD: Work around panic in FlushVCache
    
    Commit 64cc7f0ca7a44bb214396c829268a541ab286c69 created the very useful
    afs_StaleVCache() helper function, but unfortunately it also introduced
    a subtle change into how we check for whether a vcache may be a directory.
    Previously, we just used the low bit of the Fid's Vnode number, since files
    have an even number and non-files an odd number.  The new version uses
    that check but also explicitly checks `vType(avc)` against VDIR, and this new
    check involves consulting information stored in the associated vnode entry,
    not the vcache directly.  The afs_FlushVCache() implementation for
    XBSD and DARWIN NULLs removes the cross-linkage between vcache and vnode,
    so that AFSTOV(avc) becomes NULL.  Just a few lines later, it calls
    afs_StaleVCacheFlags(), at which point vType() dereferences a bad pointer
    (offset from a NULL pointer) and panics.  This would happen during shutdown,
    or other periodic reclaim/flush events that can be scheduled.
    
    Change-Id: I0800e5c743cedcbec628bfa8c8ea8978c2488c1c
    Reviewed-on: https://gerrit.openafs.org/13014
    Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
    Tested-by: BuildBot <buildbot@rampaginggeek.com>
    Reviewed-by: Andrew Deason <adeason@sinenomine.net>
    Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>

 src/afs/afs_vcache.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

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