In the Linux kernel, the following vulnerability has been resolved: fs/smb: Fix inconsistent...

In the Linux kernel, the following vulnerability has been resolved:

fs/smb: Fix inconsistent refcnt update

A possible inconsistent update of refcount was identified in smb2_compound_op.
Such inconsistent update could lead to possible resource leaks.

Why it is a possible bug:
1. In the comment section of the function, it clearly states that the
reference to cfile should be dropped after calling this function.
2. Every control flow path would check and drop the reference to
cfile, except the patched one.
3. Existing callers would not handle refcount update of cfile if
-ENOMEM is returned.

To fix the bug, an extra goto label "out" is added, to make sure that the
cleanup logic would always be respected. As the problem is caused by the
allocation failure of vars, the cleanup logic between label "finished"
and "out" can be safely ignored. According to the definition of function
is_replayable_error, the error code of "-ENOMEM" is not recoverable.
Therefore, the replay logic also gets ignored.