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OpenAdvisories
Medium · 4.4 CVE-2021-47185 EUVD-2021-33833GHSA-gvxc-64wh-vgv2

tty: tty_buffer: Fix the softlockup issue in flush_to_ldisc

Published Apr 10, 2024 · Updated May 11, 2026 · Assigned by Linux

Vendor: Linux Product: Linux Package: linux Package: linux Package: linux-allwinner-5.19 Package: linux-aws Package: linux-aws-5.0 Package: linux-aws-5.11 Package: linux-aws-5.13 Package: linux-aws-5.19 Package: linux-aws-5.3 Package: linux-aws-5.4 Package: linux-aws-5.8 Package: linux-aws-6.2 Package: linux-aws-fips Package: linux-aws-hwe Package: linux-azure Package: linux-azure-4.15 Package: linux-azure-5.11 Package: linux-azure-5.13 Package: linux-azure-5.19 Package: linux-azure-5.3 Package: linux-azure-5.4 Package: linux-azure-5.8 Package: linux-azure-6.2 Package: linux-azure-edge Package: linux-azure-fde Package: linux-azure-fde-5.19 Package: linux-azure-fde-6.2 Package: linux-azure-fips Package: linux-bluefield Package: linux-fips Package: linux-gcp Package: linux-gcp-4.15 Package: linux-gcp-5.11 Package: linux-gcp-5.13 Package: linux-gcp-5.19 Package: linux-gcp-5.3 Package: linux-gcp-5.4 Package: linux-gcp-5.8 Package: linux-gcp-6.2 Package: linux-gcp-fips Package: linux-gke Package: linux-gke-4.15 Package: linux-gke-5.15 Package: linux-gke-5.4 Package: linux-gkeop Package: linux-gkeop-5.4 Package: linux-hwe Package: linux-hwe-5.11 Package: linux-hwe-5.13 Package: linux-hwe-5.19 Package: linux-hwe-5.4 Package: linux-hwe-5.8 Package: linux-hwe-6.2 Package: linux-hwe-edge Package: linux-ibm Package: linux-ibm-5.4 Package: linux-intel-5.13 Package: linux-intel-iot-realtime Package: linux-kvm Package: linux-lowlatency-hwe-5.19 Package: linux-lowlatency-hwe-6.2 Package: linux-lts-xenial Package: linux-nvidia-6.2 Package: linux-oem Package: linux-oem-5.10 Package: linux-oem-5.13 Package: linux-oem-5.14 Package: linux-oem-5.17 Package: linux-oem-5.6 Package: linux-oem-6.0 Package: linux-oem-6.1 Package: linux-oracle Package: linux-oracle-5.0 Package: linux-oracle-5.11 Package: linux-oracle-5.13 Package: linux-oracle-5.3 Package: linux-oracle-5.4 Package: linux-oracle-5.8 Package: linux-raspi Package: linux-raspi-5.4 Package: linux-raspi-realtime Package: linux-raspi2 Package: linux-realtime Package: linux-riscv Package: linux-riscv-5.11 Package: linux-riscv-5.19 Package: linux-riscv-5.8 Package: linux-starfive-5.19 Package: linux-starfive-6.2 Package: linux-vmware Platform: Linux Ecosystem: Debian Ecosystem: Ubuntu

Description

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

tty: tty_buffer: Fix the softlockup issue in flush_to_ldisc

When running ltp testcase(ltp/testcases/kernel/pty/pty04.c) with arm64, there is a soft lockup,
which look like this one:

Workqueue: events_unbound flush_to_ldisc
Call trace:
dump_backtrace+0x0/0x1ec
show_stack+0x24/0x30
dump_stack+0xd0/0x128
panic+0x15c/0x374
watchdog_timer_fn+0x2b8/0x304
__run_hrtimer+0x88/0x2c0
__hrtimer_run_queues+0xa4/0x120
hrtimer_interrupt+0xfc/0x270
arch_timer_handler_phys+0x40/0x50
handle_percpu_devid_irq+0x94/0x220
__handle_domain_irq+0x88/0xf0
gic_handle_irq+0x84/0xfc
el1_irq+0xc8/0x180
slip_unesc+0x80/0x214 [slip]
tty_ldisc_receive_buf+0x64/0x80
tty_port_default_receive_buf+0x50/0x90
flush_to_ldisc+0xbc/0x110
process_one_work+0x1d4/0x4b0
worker_thread+0x180/0x430
kthread+0x11c/0x120

In the testcase pty04, The first process call the write syscall to send
data to the pty master. At the same time, the workqueue will do the
flush_to_ldisc to pop data in a loop until there is no more data left.
When the sender and workqueue running in different core, the sender sends
data fastly in full time which will result in workqueue doing work in loop
for a long time and occuring softlockup in flush_to_ldisc with kernel
configured without preempt. So I add need_resched check and cond_resched
in the flush_to_ldisc loop to avoid it.

Affected products

VendorProductAffectedFixed
Linux Linux 3.0 4.4.293

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 linux 5.15.5-1 —
Debian 13 linux 5.15.5-1 —
Debian 12 linux 5.15.5-1 —
ReleasePackageFixed inAdvisory
Ubuntu 24.04 LTS linux-raspi-realtime No fix yet —
Ubuntu 22.04 LTS linux-riscv +22 No fix yet —
Ubuntu 20.04 LTS linux 5.4.0-97.110 —
Ubuntu 20.04 LTS linux-aws 5.4.0-1064.67 —
Ubuntu 20.04 LTS linux-azure 5.4.0-1068.71 —
Ubuntu 20.04 LTS linux-bluefield 5.4.0-1026.29 —
Ubuntu 20.04 LTS linux-gcp 5.4.0-1063.67 —
Ubuntu 20.04 LTS linux-gke +26 No fix yet —
Ubuntu 20.04 LTS linux-gkeop 5.4.0-1032.33 —
Ubuntu 20.04 LTS linux-ibm 5.4.0-1013.14 —
Ubuntu 20.04 LTS linux-kvm 5.4.0-1054.56 —
Ubuntu 20.04 LTS linux-oracle 5.4.0-1062.66 —
Ubuntu 20.04 LTS linux-raspi 5.4.0-1052.58 —
Ubuntu 18.04 LTS linux 4.15.0-167.175 —
Ubuntu 18.04 LTS linux-aws 4.15.0-1119.127 —
Ubuntu 18.04 LTS linux-aws-5.4 5.4.0-1064.67~18.04.1 —
Ubuntu 18.04 LTS linux-azure-4.15 4.15.0-1131.144 —
Ubuntu 18.04 LTS linux-azure-5.4 5.4.0-1068.71~18.04.1 —
Ubuntu 18.04 LTS linux-gcp +14 No fix yet —
Ubuntu 18.04 LTS linux-gcp-4.15 4.15.0-1115.129 —
Ubuntu 18.04 LTS linux-gcp-5.4 5.4.0-1063.67~18.04.1 —
Ubuntu 18.04 LTS linux-hwe-5.4 5.4.0-97.110~18.04.1 —
Ubuntu 18.04 LTS linux-ibm-5.4 5.4.0-1014.15~18.04.1 —
Ubuntu 18.04 LTS linux-kvm 4.15.0-1106.108 —
Ubuntu 18.04 LTS linux-oracle 4.15.0-1086.94 —
Ubuntu 18.04 LTS linux-oracle-5.4 5.4.0-1062.66~18.04.1 —
Ubuntu 18.04 LTS linux-raspi-5.4 5.4.0-1052.58~18.04.1 —
Ubuntu 16.04 LTS linux-hwe-edge No fix yet —
Show 8 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro FIPS 20.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro FIPS 18.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro FIPS 16.04 LTS linux-fips No fix yet —
Ubuntu Pro FIPS-updates 20.04 LTS linux-aws-fips 5.4.0-1069.73+fips2 —
Ubuntu Pro FIPS-updates 20.04 LTS linux-azure-fips 5.4.0-1073.76+fips1 —
Ubuntu Pro FIPS-updates 20.04 LTS linux-fips 5.4.0-1041.47 —
Ubuntu Pro FIPS-updates 20.04 LTS linux-gcp-fips 5.4.0-1067.71~20.04.1 —
Ubuntu Pro FIPS-updates 18.04 LTS linux-aws-fips 4.15.0-2060.62 —
Ubuntu Pro FIPS-updates 18.04 LTS linux-azure-fips 4.15.0-2042.46 —
Ubuntu Pro FIPS-updates 18.04 LTS linux-fips 4.15.0-1076.85 —
Ubuntu Pro FIPS-updates 18.04 LTS linux-gcp-fips 4.15.0-2025.27 —
Ubuntu Pro FIPS-updates 16.04 LTS linux-fips No fix yet —
Ubuntu Pro 16.04 LTS linux +2 No fix yet —
Ubuntu Pro 16.04 LTS linux-aws-hwe 4.15.0-1119.126~16.04.2 —
Ubuntu Pro 16.04 LTS linux-azure 4.15.0-1130.143~16.04.1 —
Ubuntu Pro 16.04 LTS linux-gcp 4.15.0-1115.129~16.04.1 —
Ubuntu Pro 16.04 LTS linux-hwe 4.15.0-167.175~16.04.1 —
Ubuntu Pro 16.04 LTS linux-oracle 4.15.0-1086.94~16.04.1 —
Ubuntu Pro 14.04 LTS linux +2 No fix yet —
Ubuntu Pro 14.04 LTS linux-azure 4.15.0-1130.143~14.04.1 —
ReleasePackageFixed inAdvisory
RHEL 9 bpftool 7.4.0-503.11.1.el9_5 RHSA-2024:9315
RHEL 9 rv +67 5.14.0-503.11.1.el9_5 RHSA-2024:9315
RHEL 8 kernel-rt +12 4.18.0-553.5.1.rt7.346.el8_10 RHSA-2024:3627
RHEL 8 perf +26 4.18.0-553.5.1.el8_10 RHSA-2024:3618
Show 1 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
RHEL 9.4 EUS bpftool 7.3.0-427.79.1.el9_4 RHSA-2025:11810
RHEL 9.4 EUS rv +64 5.14.0-427.79.1.el9_4 RHSA-2025:11810

AlmaLinux

Errata ↗
ReleasePackageFixed inAdvisory
AlmaLinux 8 kernel-rt +11 4.18.0-553.5.1.rt7.346.el8_10 ALSA-2024:3627
AlmaLinux 8 perf +24 4.18.0-553.5.1.el8_10 ALSA-2024:3618

Rocky Linux

Errata ↗
ReleasePackageFixed inAdvisory
Rocky Linux 8 kernel 4.18.0-553.5.1.el8_10 RLSA-2024:3618
Rocky Linux 8 kernel-rt 4.18.0-553.5.1.rt7.346.el8_10 RLSA-2024:3627
ReleasePackageFixed inAdvisory
SLES 15 SP5 kernel-64kb +5 5.14.21-150500.55.62.2 SUSE-SU-2024:1659-1
SLES 15 SP5 kernel-azure +2 5.14.21-150500.33.48.1 SUSE-SU-2024:1644-1, SUSE-SU-2024:1490-1
SLES 15 SP5 kernel-default-base 5.14.21-150500.55.62.2.150500.6.27.2 SUSE-SU-2024:1659-1
SLES 15 SP5 kernel-syms 5.14.21-150500.55.62.1 SUSE-SU-2024:1659-1
SLES 15 SP4 kernel-64kb +6 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
SLES 15 SP4 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
SLES 15 SP3 kernel-64kb +7 5.3.18-150300.59.158.1 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLES 15 SP3 kernel-default-base 5.3.18-150300.59.158.1.150300.18.92.5 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLES 15 SP2 kernel-default-base 5.3.18-150200.24.188.1.150200.9.95.3 SUSE-SU-2024:1650-1, SUSE-SU-2024:1454-1
SLES 15 SP2 kernel-docs +5 5.3.18-150200.24.188.1 SUSE-SU-2024:1650-1, SUSE-SU-2024:1454-1
SLES 12 SP5 kernel-azure +2 4.12.14-16.182.1 SUSE-SU-2024:1643-1
SLES 12 SP5 kernel-docs +4 4.12.14-122.216.1 SUSE-SU-2024:1870-1
Show 22 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 15 SP4 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
SLES for SAP 15 SP4 kernel-docs +4 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
SLES for SAP 15 SP3 kernel-default-base 5.3.18-150300.59.158.1.150300.18.92.5 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLES for SAP 15 SP3 kernel-docs +5 5.3.18-150300.59.158.1 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLES for SAP 15 SP2 kernel-default-base 5.3.18-150200.24.188.1.150200.9.95.3 SUSE-SU-2024:1650-1, SUSE-SU-2024:1454-1
SLES for SAP 15 SP2 kernel-docs +5 5.3.18-150200.24.188.1 SUSE-SU-2024:1650-1, SUSE-SU-2024:1454-1
SLES for SAP 12 SP5 kernel-azure +2 4.12.14-16.182.1 SUSE-SU-2024:1643-1
SLES for SAP 12 SP5 kernel-syms +2 4.12.14-122.216.1 SUSE-SU-2024:1870-1
SLE Real Time 12 SP5 kernel-rt +3 4.12.14-10.182.1 SUSE-SU-2024:1646-1
SLE Micro 5.5 kernel-default 5.14.21-150500.55.62.2 SUSE-SU-2024:1659-1
SLE Micro 5.5 kernel-default-base 5.14.21-150500.55.62.2.150500.6.27.2 SUSE-SU-2024:1659-1
SLE Micro 5.5 kernel-rt +1 5.14.21-150500.13.52.1 SUSE-SU-2024:1663-1
SLE Micro 5.4 kernel-default 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
SLE Micro 5.4 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
SLE Micro 5.4 kernel-rt +1 5.14.21-150400.15.79.1 SUSE-SU-2024:1647-1
SLE Micro 5.3 kernel-default 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
SLE Micro 5.3 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
SLE Micro 5.3 kernel-rt +1 5.14.21-150400.15.79.1 SUSE-SU-2024:1647-1
SLE Micro 5.2 kernel-default 5.3.18-150300.59.158.1 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLE Micro 5.2 kernel-default-base 5.3.18-150300.59.158.1.150300.18.92.5 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLE Micro 5.2 kernel-rt +1 5.3.18-150300.166.1 SUSE-SU-2024:1465-1
SLE Micro 5.1 kernel-default 5.3.18-150300.59.158.1 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLE Micro 5.1 kernel-default-base 5.3.18-150300.59.158.1.150300.18.92.5 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLE Micro 5.1 kernel-rt +1 5.3.18-150300.166.1 SUSE-SU-2024:1465-1
SLE Live Patching 15 SP5 kernel-default 5.14.21-150500.55.62.2 SUSE-SU-2024:1659-1
SLE Live Patching 15 SP5 kernel-livepatch-SLE15-SP5-RT_Update_14 1-150500.11.5.1 SUSE-SU-2024:1663-1
SLE Live Patching 15 SP5 kernel-livepatch-SLE15-SP5_Update_13 1-150500.11.3.2 SUSE-SU-2024:1659-1
SLE Live Patching 15 SP4 kernel-default 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
SLE Live Patching 15 SP4 kernel-livepatch-SLE15-SP4_Update_26 1-150400.9.3.1 SUSE-SU-2024:1641-1
SLE Live Patching 15 SP3 kernel-default 5.3.18-150300.59.158.1 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLE Live Patching 15 SP3 kernel-livepatch-SLE15-SP3_Update_43 1-150300.7.3.5 SUSE-SU-2024:1489-1
SLE Live Patching 15 SP3 kernel-livepatch-SLE15-SP3_Update_44 1-150300.7.3.1 SUSE-SU-2024:1642-1
SLE Live Patching 15 SP2 kernel-default 5.3.18-150200.24.188.1 SUSE-SU-2024:1650-1, SUSE-SU-2024:1454-1
SLE Live Patching 15 SP2 kernel-livepatch-SLE15-SP2_Update_47 1-150200.5.3.3 SUSE-SU-2024:1454-1
SLE Live Patching 15 SP2 kernel-livepatch-SLE15-SP2_Update_48 1-150200.5.3.1 SUSE-SU-2024:1650-1
SLE Live Patching 12 SP5 kernel-default 4.12.14-122.216.1 SUSE-SU-2024:1870-1
SLE Live Patching 12 SP5 kgraft-patch-SLE12-SP5_Update_56 1-8.3.1 SUSE-SU-2024:1870-1
SLE HPC 15 SP4 kernel-64kb +5 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
SLE HPC 15 SP4 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
SLE HPC 15 SP3 kernel-64kb +6 5.3.18-150300.59.158.1 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLE HPC 15 SP3 kernel-default-base 5.3.18-150300.59.158.1.150300.18.92.5 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SLE HPC 15 SP2 kernel-default-base 5.3.18-150200.24.188.1.150200.9.95.3 SUSE-SU-2024:1650-1, SUSE-SU-2024:1454-1
SLE HPC 15 SP2 kernel-docs +5 5.3.18-150200.24.188.1 SUSE-SU-2024:1650-1, SUSE-SU-2024:1454-1
SUSE Real Time Module 15 SP5 kernel-rt +3 5.14.21-150500.13.52.1 SUSE-SU-2024:1663-1
SUSE Manager Server 4.3 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
SUSE Manager Server 4.3 kernel-syms +3 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
SUSE Manager Proxy 4.3 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
SUSE Manager Proxy 4.3 kernel-syms +2 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
SUSE Enterprise Storage 7.1 kernel-64kb +6 5.3.18-150300.59.158.1 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
SUSE Enterprise Storage 7.1 kernel-default-base 5.3.18-150300.59.158.1.150300.18.92.5 SUSE-SU-2024:1642-1, SUSE-SU-2024:1489-1
ReleasePackageFixed inAdvisory
openSUSE Leap 15.5 dtb-aarch64 +2 5.14.21-150500.55.62.1 SUSE-SU-2024:1659-1
openSUSE Leap 15.5 kernel-64kb +7 5.14.21-150500.55.62.2 SUSE-SU-2024:1659-1
openSUSE Leap 15.5 kernel-azure +2 5.14.21-150500.33.48.1 SUSE-SU-2024:1644-1, SUSE-SU-2024:1490-1
openSUSE Leap 15.5 kernel-default-base 5.14.21-150500.55.62.2.150500.6.27.2 SUSE-SU-2024:1659-1
openSUSE Leap 15.5 kernel-rt +3 5.14.21-150500.13.52.1 SUSE-SU-2024:1663-1
Show 2 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
openSUSE Leap Micro 5.4 kernel-default 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
openSUSE Leap Micro 5.4 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
openSUSE Leap Micro 5.4 kernel-rt 5.14.21-150400.15.79.1 SUSE-SU-2024:1647-1
openSUSE Leap Micro 5.3 kernel-default 5.14.21-150400.24.119.1 SUSE-SU-2024:1641-1
openSUSE Leap Micro 5.3 kernel-default-base 5.14.21-150400.24.119.1.150400.24.56.1 SUSE-SU-2024:1641-1
openSUSE Leap Micro 5.3 kernel-rt 5.14.21-150400.15.79.1 SUSE-SU-2024:1647-1

Amazon Linux

ReleasePackageFixed inAdvisory
Amazon Linux 2 kernel-livepatch-4.14.256-197.484 1.0-0.amzn2 ALAS2-2025-2752, ALAS2-2021-1727
Amazon Linux 2 perf +8 4.14.256-197.484.amzn2 ALAS2-2025-2752, ALAS2-2021-1727

Oracle Linux

ReleasePackageFixed inAdvisory
Oracle Linux 9 bpftool 7.4.0-503.11.1.el9_5 ELSA-2024-9315
Oracle Linux 9 rv +28 5.14.0-503.11.1.el9_5 ELSA-2024-9315
Oracle Linux 8 perf +19 4.18.0-553.5.1.el8_10 ELSA-2024-3618

Advisories 28

References