linux-cve-announce - CVE-2023-53511: io_uring: fix fget leak when fs don't support nowait buffered read

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Message-ID: <2025100130-CVE-2023-53511-99e8@gregkh>
Date: Wed,  1 Oct 2025 13:46:03 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53511: io_uring: fix fget leak when fs don't support nowait buffered read

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

The Linux kernel CVE team has assigned CVE-2023-53511 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.18 with commit a196c78b5443fc61af2c0490213b9d125482cbd1 and fixed in 6.1.16 with commit 75a499fc9d66a32271e2b3e4ca71156e8ad3b484
	Issue introduced in 5.18 with commit a196c78b5443fc61af2c0490213b9d125482cbd1 and fixed in 6.2.3 with commit 10fb2e16ee6ffaf1716b9e90d007e6b300bfa457
	Issue introduced in 5.18 with commit a196c78b5443fc61af2c0490213b9d125482cbd1 and fixed in 6.3 with commit 54aa7f2330b82884f4a1afce0220add6e8312f8b
	Issue introduced in 5.17.9 with commit cef27a7d36026bd3c86f4fdfb4611ebbe2814af4

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2023-53511
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	io_uring/io_uring.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/75a499fc9d66a32271e2b3e4ca71156e8ad3b484
	https://git.kernel.org/stable/c/10fb2e16ee6ffaf1716b9e90d007e6b300bfa457
	https://git.kernel.org/stable/c/54aa7f2330b82884f4a1afce0220add6e8312f8b