CVE-2021-47317

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

powerpc/bpf: Fix detecting BPF atomic instructions

Commit 91c960b0056672 ("bpf: Rename BPF_XADD and prepare to encode other

atomics in .imm") converted BPF_XADD to BPF_ATOMIC and added a way to

distinguish instructions based on the immediate field. Existing JIT

implementations were updated to check for the immediate field and to

reject programs utilizing anything more than BPF_ADD (such as BPF_FETCH)

in the immediate field.

However, the check added to powerpc64 JIT did not look at the correct

BPF instruction. Due to this, such programs would be accepted and

incorrectly JIT'ed resulting in soft lockups, as seen with the atomic

bounds test. Fix this by looking at the correct immediate value.