• Thomas Hebb's avatar
    hfsplus: don't store special "osx" xattr prefix on-disk · 2e15dca2
    Thomas Hebb authored
    commit db579e76 upstream.
    
    On Mac OS X, HFS+ extended attributes are not namespaced.  Since we want
    to be compatible with OS X filesystems and yet still support the Linux
    namespacing system, the hfsplus driver implements a special "osx"
    namespace that is reported for any attribute that is not namespaced
    on-disk.  However, the current code for getting and setting these
    unprefixed attributes is broken.
    
    hfsplus_osx_setattr() and hfsplus_osx_getattr() are passed names that have
    already had their "osx." prefixes stripped by the generic functions.  The
    functions first, quite correctly, check those names to make sure that they
    aren't prefixed with a known namespace, which would allow namespace access
    restrictions to be bypassed.  However, the functions then prepend "osx."
    to the name they're given before passing it on to hfsplus_getattr() and
    hfsplus_setattr().  Not only does this cause the "osx." prefix to be
    stored on-disk, defeating its purpose, it also breaks the check for the
    special "com.apple.FinderInfo" attribute, which is reported for all files,
    and as a consequence makes some userspace applications (e.g.  GNU patch)
    fail even when extended attributes are not otherwise in use.
    
    There are five commits which have touched this particular code:
    
      127e5f5a ("hfsplus: rework functionality of getting, setting and deleting of extended attributes")
      b168fff7 ("hfsplus: use xattr handlers for removexattr")
      bf29e886 ("hfsplus: correct usage of HFSPLUS_ATTR_MAX_STRLEN for non-English attributes")
      fcacbd95e121 ("fs/hfsplus: move xattr_name allocation in hfsplus_getxattr()")
      ec1bbd346f18 ("fs/hfsplus: move xattr_name allocation in hfsplus_setxattr()")
    
    The first commit creates the functions to begin with.  The namespace is
    prepended by the original code, which I believe was correct at the time,
    since hfsplus_?etattr() stripped the prefix if found.  The second commit
    removes this behavior from hfsplus_?etattr() and appears to have been
    intended to also remove the prefixing from hfsplus_osx_?etattr().
    However, what it actually does is remove a necessary strncpy() call
    completely, breaking the osx namespace entirely.  The third commit re-adds
    the strncpy() call as it was originally, but doesn't mention it in its
    commit message.  The final two commits refactor the code and don't affect
    its functionality.
    
    This commit does what b168fff7 attempted to do (prevent the prefix from
    being added), but does it properly, instead of passing in an empty buffer
    (which is what b168fff7 actually did).
    
    Fixes: b168fff7 ("hfsplus: use xattr handlers for removexattr")
    Signed-off-by: default avatarThomas Hebb <tommyhebb@gmail.com>
    Cc: Hin-Tak Leung <htl10@users.sourceforge.net>
    Cc: Sergei Antonov <saproj@gmail.com>
    Cc: Anton Altaparmakov <anton@tuxera.com>
    Cc: Fabian Frederick <fabf@skynet.be>
    Cc: Christian Kujau <lists@nerdbynature.de>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Viacheslav Dubeyko <slava@dubeyko.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: default avatarThomas Hebb <tommyhebb@gmail.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    2e15dca2
xattr.c 22.8 KB