Bug 2360931 (CVE-2025-37893)

Summary: CVE-2025-37893 kernel: LoongArch: BPF: Fix off-by-one error in build_prologue()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
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Hardware: All   
OS: Linux   
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Description OSIDB Bzimport 2025-04-18 08:01:45 UTC 
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.
Comment 1 Avinash Hanwate 2025-04-18 12:58:10 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025041816-CVE-2025-37893-57b4@gregkh/T