CVE-2025-37893: LoongArch: BPF: Fix off-by-one error in build_prologue()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-04-18 · updated 2026-07-30
Weakness: CWE-193

Description

In the Linux kernel, the following vulnerability has been resolved: LoongArch: BPF: Fix off-by-one error in build_prologue() Vincent reported that running BPF progs with tailcalls on LoongArch causes kernel hard lockup. Debugging the issues shows that the JITed image missing a jirl instruction at the end of the epilogue. There are two passes in JIT compiling, the first pass set the flags and the second pass generates JIT code based on those flags. With BPF progs mixing bpf2bpf and tailcalls, build_prologue() generates N insns in the first pass and then generates N+1 insns in the second pass. This makes epilogue_offset off by one and we will jump to some unexpected insn and cause lockup. Fix this by inserting a nop insn.

Affected products

Linux kernel: from 6.1 before 6.1.134; from 6.2 before 6.6.87; from 6.7 before 6.12.23; from 6.13 before 6.13.11; from 6.14 before 6.14.2 — fixed in 6.1.134, 6.12.23, 6.13.11, 6.14.2, 6.6.87

How to fix

Upgrade to a fixed version: Linux kernel 6.1.134, 6.12.23, 6.13.11, 6.14.2. Check the vendor advisory for mitigations.

References

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