// For flags

CVE-2021-47185

tty: tty_buffer: Fix the softlockup issue in flush_to_ldisc

Severity Score

4.4
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track
*SSVC
Descriptions

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.

*Credits: N/A
CVSS Scores
Attack Vector
Local
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
* Common Vulnerability Scoring System
SSVC
  • Decision:Track
Exploitation
None
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2024-03-25 CVE Reserved
  • 2024-04-10 CVE Published
  • 2024-04-11 EPSS Updated
  • 2024-12-19 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-1050: Excessive Platform Resource Consumption within a Loop
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
< 4.4.293
Search vendor "Linux" for product "Linux Kernel" and version " < 4.4.293"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
< 4.9.291
Search vendor "Linux" for product "Linux Kernel" and version " < 4.9.291"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
< 4.14.256
Search vendor "Linux" for product "Linux Kernel" and version " < 4.14.256"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
< 4.19.218
Search vendor "Linux" for product "Linux Kernel" and version " < 4.19.218"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
< 5.4.162
Search vendor "Linux" for product "Linux Kernel" and version " < 5.4.162"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
< 5.10.82
Search vendor "Linux" for product "Linux Kernel" and version " < 5.10.82"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
< 5.15.5
Search vendor "Linux" for product "Linux Kernel" and version " < 5.15.5"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
< 5.16
Search vendor "Linux" for product "Linux Kernel" and version " < 5.16"
en
Affected