CVE-2025-39819

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.