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

What is CVE-2023-53511?

CVE-2023-53511 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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/[email protected]/T/#t

Weakness: CWE-401

Which versions are affected by CVE-2023-53511?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2023-53511?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2023-53511 being exploited?

There is no known exploitation of CVE-2023-53511 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2023-53511, DEBIAN-CVE-2023-53511, GHSA-m97q-c3xf-55xf, UBUNTU-CVE-2023-53511.