The (1) real_lookup and (2) __lookup_hash functions in fs/namei.c in the vfs implementation in the Linux kernel before 2.6.25.15 do not prevent creation of a child dentry for a deleted (aka S_DEAD) directory, which allows local users to cause a denial of service ("overflow" of the UBIFS orphan area) via a series of attempted file creations within deleted directories.
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.