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

kfence: fix memory leak when cat kfence objects

Hulk robot reported a kmemleak problem:

unreferenced object 0xffff93d1d8cc02e8 (size 248):
comm "cat", pid 23327, jiffies 4624670141 (age 495992.217s)
hex dump (first 32 bytes):
00 40 85 19 d4 93 ff ff 00 10 00 00 00 00 00 00 .@..............
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
seq_open+0x2a/0x80
full_proxy_open+0x167/0x1e0
do_dentry_open+0x1e1/0x3a0
path_openat+0x961/0xa20
do_filp_open+0xae/0x120
do_sys_openat2+0x216/0x2f0
do_sys_open+0x57/0x80
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
unreferenced object 0xffff93d419854000 (size 4096):
comm "cat", pid 23327, jiffies 4624670141 (age 495992.217s)
hex dump (first 32 bytes):
6b 66 65 6e 63 65 2d 23 32 35 30 3a 20 30 78 30 kfence-#250: 0x0
30 30 30 30 30 30 30 37 35 34 62 64 61 31 32 2d 0000000754bda12-
backtrace:
seq_read_iter+0x313/0x440
seq_read+0x14b/0x1a0
full_proxy_read+0x56/0x80
vfs_read+0xa5/0x1b0
ksys_read+0xa0/0xf0
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9

I find that we can easily reproduce this problem with the following
commands:

cat /sys/kernel/debug/kfence/objects
echo scan > /sys/kernel/debug/kmemleak
cat /sys/kernel/debug/kmemleak

The leaked memory is allocated in the stack below:

do_syscall_64
do_sys_open
do_dentry_open
full_proxy_open
seq_open ---> alloc seq_file
vfs_read
full_proxy_read
seq_read
seq_read_iter
traverse ---> alloc seq_buf

And it should have been released in the following process:

do_syscall_64
syscall_exit_to_user_mode
exit_to_user_mode_prepare
task_work_run
____fput
__fput
full_proxy_release ---> free here

However, the release function corresponding to file_operations is not
implemented in kfence. As a result, a memory leak occurs. Therefore,
the solution to this problem is to implement the corresponding release
function.
Published: 2024-03-04
Score: 3.3 Low
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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Tracking

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History

Fri, 04 Apr 2025 15:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-401
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.16:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.16:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.16:rc6:*:*:*:*:*:*

Thu, 31 Oct 2024 14:15:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

cvssV3_1

{'score': 3.3, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L'}


Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-05-04T07:03:54.349Z

Reserved: 2024-02-29T22:33:44.300Z

Link: CVE-2021-47089

cve-icon Vulnrichment

Updated: 2024-08-04T05:24:39.939Z

cve-icon NVD

Status : Analyzed

Published: 2024-03-04T18:15:07.560

Modified: 2025-04-04T14:41:46.367

Link: CVE-2021-47089

cve-icon Redhat

Severity : Low

Publid Date: 2024-03-04T00:00:00Z

Links: CVE-2021-47089 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses