CVE-2026-92517bpf, riscv: Fix extable handling for arena load_acquire

Official description

In the Linux kernel, the following vulnerability has been resolved: bpf, riscv: Fix extable handling for arena load_acquire emit_atomic_ld_st() returns 1 to have build_body() skip the zext after a sub-word load_acquire. The caller does "ret = ret ?: add_exception_handler(...)", which skips add_exception_handler() on any non-zero ret, so the extable entry is missing and a faulting PROBE_ATOMIC load_acquire oopses. REG_DONT_CLEAR_MARKER leaves rd stale on fault, and the verifier still thinks the load overwrote it, so a program can leak it through a map. Check ret >= 0 before calling add_exception_handler(), and pass rd for LOAD_ACQ so the fault zeroes rd like a PROBE_MEM load. Return ret unchanged for the zext skip.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/26d9496c826586338d1b8c27edfec4a19a89f462
• https://git.kernel.org/stable/c/08fe2eaa609180c1baeb76c2629a9c82263b0427
• https://git.kernel.org/stable/c/5eb8921371c6fd117d4a328b6053dfda38707df8