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

LoongArch: BPF: Fix jump offset calculation in tailcall

The extra pass of bpf_int_jit_compile() skips JIT context initialization
which essentially skips offset calculation leaving out_offset = -1, so
the jmp_offset in emit_bpf_tail_call is calculated by

"#define jmp_offset (out_offset - (cur_offset))"

is a negative number, which is wrong. The final generated assembly are
as follow.

54: bgeu $a2, $t1, -8 # 0x0000004c
58: addi.d $a6, $s5, -1
5c: bltz $a6, -16 # 0x0000004c
60: alsl.d $t2, $a2, $a1, 0x3
64: ld.d $t2, $t2, 264
68: beq $t2, $zero, -28 # 0x0000004c

Before apply this patch, the follow test case will reveal soft lock issues.

cd tools/testing/selftests/bpf/
./test_progs --allow=tailcalls/tailcall_bpf2bpf_1

dmesg:
watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [test_progs:25056]
History

Fri, 05 Sep 2025 14:15:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
Vendors & Products Linux
Linux linux Kernel

Fri, 05 Sep 2025 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate


Thu, 04 Sep 2025 15:45:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: LoongArch: BPF: Fix jump offset calculation in tailcall The extra pass of bpf_int_jit_compile() skips JIT context initialization which essentially skips offset calculation leaving out_offset = -1, so the jmp_offset in emit_bpf_tail_call is calculated by "#define jmp_offset (out_offset - (cur_offset))" is a negative number, which is wrong. The final generated assembly are as follow. 54: bgeu $a2, $t1, -8 # 0x0000004c 58: addi.d $a6, $s5, -1 5c: bltz $a6, -16 # 0x0000004c 60: alsl.d $t2, $a2, $a1, 0x3 64: ld.d $t2, $t2, 264 68: beq $t2, $zero, -28 # 0x0000004c Before apply this patch, the follow test case will reveal soft lock issues. cd tools/testing/selftests/bpf/ ./test_progs --allow=tailcalls/tailcall_bpf2bpf_1 dmesg: watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [test_progs:25056]
Title LoongArch: BPF: Fix jump offset calculation in tailcall
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-09-04T15:33:16.547Z

Reserved: 2025-04-16T04:51:24.033Z

Link: CVE-2025-38723

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-09-04T16:15:42.130

Modified: 2025-09-05T17:47:24.833

Link: CVE-2025-38723

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-09-04T00:00:00Z

Links: CVE-2025-38723 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-09-05T14:02:32Z