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    9pfs: allocate space for guest originated empty strings · ba42ebb8
    Li Qiang 提交于
    If a guest sends an empty string paramater to any 9P operation, the current
    code unmarshals it into a V9fsString equal to { .size = 0, .data = NULL }.
    
    This is unfortunate because it can cause NULL pointer dereference to happen
    at various locations in the 9pfs code. And we don't want to check str->data
    everywhere we pass it to strcmp() or any other function which expects a
    dereferenceable pointer.
    
    This patch enforces the allocation of genuine C empty strings instead, so
    callers don't have to bother.
    
    Out of all v9fs_iov_vunmarshal() users, only v9fs_xattrwalk() checks if
    the returned string is empty. It now uses v9fs_string_size() since
    name.data cannot be NULL anymore.
    Signed-off-by: NLi Qiang <liqiang6-s@360.cn>
    [groug, rewritten title and changelog,
     fix empty string check in v9fs_xattrwalk()]
    Signed-off-by: NGreg Kurz <groug@kaod.org>
    ba42ebb8
9p-iov-marshal.c 10.1 KB