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CVE-2021-47608— bpf: Fix kernel address leakage in atomic fetch

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，该漏洞源于对check_mem_access()处理的更改存在问题，该问题允许非特权用户泄露内核指针。

AI Predicted 7.8 Difficulty: Hard EPSS 0.21% · P11

Affected Version Matrix 6

VendorProduct Version RangeStatus
Linux Linux 37086bfdc737ea6f66bf68dcf16757004d68e1e1< 423628125a484538111c2c6d9bb1588eb086053b affected
37086bfdc737ea6f66bf68dcf16757004d68e1e1< 7d3baf0afa3aa9102d6a521a8e4c41888bb79882 affected
5.12 affected
< 5.12 unaffected
5.15.11≤ 5.15.* unaffected
5.16≤ * unaffected
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I. Basic Information for CVE-2021-47608

Vulnerability Information
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Vulnerability Title
bpf: Fix kernel address leakage in atomic fetch
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix kernel address leakage in atomic fetch The change in commit 37086bfdc737 ("bpf: Propagate stack bounds to registers in atomics w/ BPF_FETCH") around check_mem_access() handling is buggy since this would allow for unprivileged users to leak kernel pointers. For example, an atomic fetch/and with -1 on a stack destination which holds a spilled pointer will migrate the spilled register type into a scalar, which can then be exported out of the program (since scalar != pointer) by dumping it into a map value. The original implementation of XADD was preventing this situation by using a double call to check_mem_access() one with BPF_READ and a subsequent one with BPF_WRITE, in both cases passing -1 as a placeholder value instead of register as per XADD semantics since it didn't contain a value fetch. The BPF_READ also included a check in check_stack_read_fixed_off() which rejects the program if the stack slot is of __is_pointer_value() if dst_regno < 0. The latter is to distinguish whether we're dealing with a regular stack spill/ fill or some arithmetical operation which is disallowed on non-scalars, see also 6e7e63cbb023 ("bpf: Forbid XADD on spilled pointers for unprivileged users") for more context on check_mem_access() and its handling of placeholder value -1. One minimally intrusive option to fix the leak is for the BPF_FETCH case to initially check the BPF_READ case via check_mem_access() with -1 as register, followed by the actual load case with non-negative load_reg to propagate stack bounds to registers.
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，该漏洞源于对check_mem_access()处理的更改存在问题，该问题允许非特权用户泄露内核指针。
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 37086bfdc737ea6f66bf68dcf16757004d68e1e1 ~ 423628125a484538111c2c6d9bb1588eb086053b -
Linux Linux 5.12 -

II. Public POCs for CVE-2021-47608

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III. Intelligence Information for CVE-2021-47608

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Other References for CVE-2021-47608 (1)

Same Patch Batch · Linux · 2024-06-19 · 122 CVEs total

CVE-2024-38558 10.0 CRITICAL net: openvswitch: fix overwriting ct original tuple for ICMPv6
CVE-2024-38570 9.8 CRITICAL gfs2: Fix potential glock use-after-free on unmount
CVE-2021-47587 9.8 CRITICAL net: systemport: Add global locking for descriptor lifecycle
CVE-2024-38544 9.8 CRITICAL RDMA/rxe: Fix seg fault in rxe_comp_queue_pkt
CVE-2021-47611 8.1 HIGH mac80211: validate extended element ID is present
CVE-2024-38587 7.8 HIGH speakup: Fix sizeof() vs ARRAY_SIZE() bug
CVE-2024-38556 7.8 HIGH net/mlx5: Add a timeout to acquire the command queue semaphore
CVE-2024-38610 7.8 HIGH drivers/virt/acrn: fix PFNMAP PTE checks in acrn_vm_ram_map()
CVE-2024-38605 7.8 HIGH ALSA: core: Fix NULL module pointer assignment at card init
CVE-2024-38599 7.8 HIGH jffs2: prevent xattr node from overflowing the eraseblock
CVE-2024-38592 7.8 HIGH drm/mediatek: Init `ddp_comp` with devm_kcalloc()
CVE-2024-38564 7.8 HIGH bpf: Add BPF_PROG_TYPE_CGROUP_SKB attach type enforcement in BPF_LINK_CREATE
CVE-2024-38568 7.8 HIGH drivers/perf: hisi: hns3: Fix out-of-bound access when valid event group
CVE-2024-38572 7.8 HIGH wifi: ath12k: fix out-of-bound access of qmi_invoke_handler()
CVE-2024-38578 7.8 HIGH ecryptfs: Fix buffer size for tag 66 packet
CVE-2024-38580 7.8 HIGH epoll: be better about file lifetimes
CVE-2024-38569 7.8 HIGH drivers/perf: hisi_pcie: Fix out-of-bound access when valid event group
CVE-2024-38583 7.8 HIGH nilfs2: fix use-after-free of timer for log writer thread
CVE-2024-38614 7.8 HIGH openrisc: traps: Don't send signals to kernel mode threads
CVE-2024-38588 7.8 HIGH ftrace: Fix possible use-after-free issue in ftrace_location()

Showing top 20 of 122 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2021-47608

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