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    Subject[PATCH 5.13 255/351] powerpc/bpf: Fix detecting BPF atomic instructions
    Date
    From: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

    [ Upstream commit 419ac821766cbdb9fd85872bb3f1a589df05c94c ]

    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.

    Fixes: 91c960b0056672 ("bpf: Rename BPF_XADD and prepare to encode other atomics in .imm")
    Reported-by: Jiri Olsa <jolsa@redhat.com>
    Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
    Tested-by: Jiri Olsa <jolsa@redhat.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/4117b430ffaa8cd7af042496f87fd7539e4f17fd.1625145429.git.naveen.n.rao@linux.vnet.ibm.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/net/bpf_jit_comp64.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
    index 57a8c1153851..94411af24013 100644
    --- a/arch/powerpc/net/bpf_jit_comp64.c
    +++ b/arch/powerpc/net/bpf_jit_comp64.c
    @@ -667,7 +667,7 @@ emit_clear:
    * BPF_STX ATOMIC (atomic ops)
    */
    case BPF_STX | BPF_ATOMIC | BPF_W:
    - if (insn->imm != BPF_ADD) {
    + if (imm != BPF_ADD) {
    pr_err_ratelimited(
    "eBPF filter atomic op code %02x (@%d) unsupported\n",
    code, i);
    @@ -689,7 +689,7 @@ emit_clear:
    PPC_BCC_SHORT(COND_NE, tmp_idx);
    break;
    case BPF_STX | BPF_ATOMIC | BPF_DW:
    - if (insn->imm != BPF_ADD) {
    + if (imm != BPF_ADD) {
    pr_err_ratelimited(
    "eBPF filter atomic op code %02x (@%d) unsupported\n",
    code, i);
    --
    2.30.2


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