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Fencer Vulns
medium 5.5

CVE-2021-47119 json

ext4: fix memory leak in ext4_fill_super

published 2024-03-15 2 y ago modified 2026-06-17 4 mo ago also EUVD-2021-33767

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

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

ext4: fix memory leak in ext4_fill_super

Buffer head references must be released before calling kill_bdev(); otherwise the buffer head (and its page referenced by b_data) will not be freed by kill_bdev, and subsequently that bh will be leaked.

If blocksizes differ, sb_set_blocksize() will kill current buffers and page cache by using kill_bdev(). And then super block will be reread again but using correct blocksize this time. sb_set_blocksize() didn't fully free superblock page and buffer head, and being busy, they were not freed and instead leaked.

This can easily be reproduced by calling an infinite loop of:

systemctl start <ext4_on_lvm>.mount, and systemctl stop <ext4_on_lvm>.mount

... since systemd creates a cgroup for each slice which it mounts, and the bh leak get amplified by a dying memory cgroup that also never gets freed, and memory consumption is much more easily noticed.

Patch / fix

  • Linux Linux 5.10.43, 5.12.10, 5.13
  • linux Debian 14, Debian 13, Debian 12 5.10.46-1

debian advisories DEBIAN-CVE-2021-47119

  • linux Ubuntu 20.04 LTS 5.4.0-214.234
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1144.154
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1147.156
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1090.95
  • linux-iot Ubuntu 20.04 LTS 5.4.0-1049.52
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1131.140
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1149.156
  • linux-raspi Ubuntu 20.04 LTS 5.4.0-1129.142

ubuntu advisories UBUNTU-CVE-2021-47119

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.216.1
  • kernel-source SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.216.1
  • kernel-default SLES for SAP 12 SP5, SLES 12 SP5, SLE Workstation Extension 12 SP5 +2 more 4.12.14-122.216.1
  • kernel-obs-build SLE Software Development Kit 12 SP5 4.12.14-122.216.1
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.182.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.182.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.182.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.182.1

suse advisories SUSE-SU-2024:1870-1SUSE-SU-2024:1646-1SUSE-SU-2024:1643-1SUSE-SU-2024:1489-1SUSE-SU-2024:1465-1SUSE-SU-2024:1454-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-47119 updated cvss 4.1

kernel: ext4: fix memory leak in ext4_fill_super

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 y ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-401 Missing Release of Memory after Effective Lifetime
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.