io_uring: fix fget leak when fs don't support nowait buffered read

{
  "id": "857bcfc1629f5753fce65f658ab00a68c6f2b49592d998bb10baa8b8abc8a49e",
  "url": "https://osv.dev/vulnerability/CVE-2023-53511",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "io_uring: fix fget leak when fs don't support nowait buffered read",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: io_uring: fix fget leak when fs don't support nowait buffered read Heming reported a BUG when using io_uring doing link-cp on ocfs2. [1] Do the following steps can reproduce this BUG: mount -t ocfs2 /dev/vdc /mnt/ocfs2 cp testfile /mnt/ocfs2/ ./link-cp /mnt/ocfs2/testfile /mnt/ocfs2/testfile.1 umount /mnt/ocfs2 Then umount will fail, and it outputs: umount: /mnt/ocfs2: target is busy. While tracing umount, it blames mnt_get_count() not return as expected. Do a deep investigation for fget()/fput() on related code flow, I've finally found that fget() leaks since ocfs2 doesn't support nowait buffered read. io_issue_sqe |-io_assign_file // do fget() first |-io_read |-io_iter_do_read |-ocfs2_file_read_iter // return -EOPNOTSUPP |-kiocb_done |-io_rw_done |-__io_complete_rw_common // set REQ_F_REISSUE |-io_resubmit_prep |-io_req_prep_async // override req->file, leak happens This was introduced by commit a196c78b5443 in v5.18. Fix it by don't re-assign req->file if it has already been assigned. [1] https://lore.kernel.org/ocfs2-devel/ab580a75-91c8-d68a-3455-40361be1bfa8@linux.alibaba.com/T/#t",
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      "modified": "2026-10-28T02:30:26.751076706Z",
      "provider": "osv",
      "references": [
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  "source_id": "core-osv",
  "document_id": 493196,
  "published_at": "2025-10-01T11:46:00.185+00:00"
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