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CVE-2021-47089— kfence: fix memory leak when cat kfence objects

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于kfence中的cat kfence存在内存泄漏。

AI Predicted 5.5 Difficulty: Theoretical EPSS 0.19% · P8

Possible ATT&CK Techniques 1 AI

T1608 · Stage Capabilities

Affected Version Matrix 6

VendorProduct Version RangeStatus
Linux Linux 0ce20dd840897b12ae70869c69f1ba34d6d16965< 2f06c8293d27f6337f907042c602c9c953988c48 affected
0ce20dd840897b12ae70869c69f1ba34d6d16965< 0129ab1f268b6cf88825eae819b9b84aa0a85634 affected
5.12 affected
< 5.12 unaffected
5.15.12≤ 5.15.* unaffected
5.16≤ * unaffected
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I. Basic Information for CVE-2021-47089

Vulnerability Information
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Vulnerability Title
kfence: fix memory leak when cat kfence objects
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于kfence中的cat kfence存在内存泄漏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 0ce20dd840897b12ae70869c69f1ba34d6d16965 ~ 2f06c8293d27f6337f907042c602c9c953988c48 -
Linux Linux 5.12 -

II. Public POCs for CVE-2021-47089

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III. Intelligence Information for CVE-2021-47089

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Other References for CVE-2021-47089 (2)

Same Patch Batch · Linux · 2024-03-04 · 26 CVEs total

CVE-2021-47107 9.8 CRITICAL NFSD: Fix READDIR buffer overflow
CVE-2021-47103 9.8 CRITICAL inet: fully convert sk->sk_rx_dst to RCU rules
CVE-2021-47082 7.8 HIGH tun: avoid double free in tun_free_netdev
CVE-2021-47087 7.8 HIGH tee: optee: Fix incorrect page free bug
CVE-2021-47106 7.8 HIGH netfilter: nf_tables: fix use-after-free in nft_set_catchall_destroy()
CVE-2021-47094 7.8 HIGH KVM: x86/mmu: Don't advance iterator after restart due to yielding
CVE-2021-47099 7.8 HIGH veth: ensure skb entering GRO are not cloned.
CVE-2021-47083 7.1 HIGH pinctrl: mediatek: fix global-out-of-bounds issue
CVE-2021-47102 7.1 HIGH net: marvell: prestera: fix incorrect structure access
CVE-2021-47096 ALSA: rawmidi - fix the uninitalized user_pversion
CVE-2021-47108 drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf
CVE-2021-47105 ice: xsk: return xsk buffers back to pool when cleaning the ring
CVE-2021-47104 IB/qib: Fix memory leak in qib_user_sdma_queue_pkts()
CVE-2021-47101 asix: fix uninit-value in asix_mdio_read()
CVE-2021-47100 ipmi: Fix UAF when uninstall ipmi_si and ipmi_msghandler module
CVE-2021-47098 hwmon: (lm90) Prevent integer overflow/underflow in hysteresis calculations
CVE-2021-47097 Input: elantech - fix stack out of bound access in elantech_change_report_id()
CVE-2024-26622 tomoyo: fix UAF write bug in tomoyo_write_control()
CVE-2021-47095 ipmi: ssif: initialize ssif_info->client early
CVE-2021-47093 platform/x86: intel_pmc_core: fix memleak on registration failure

Showing top 20 of 26 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2021-47089

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