On Thu, Jul 01, 2021 at 08:38:58PM +0530, Naveen N. Rao wrote:
> 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 <jo...@redhat.com>
> Tested-by: Jiri Olsa <jo...@redhat.com>
> Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> ---
> Hi Jiri,
> FYI: I made a small change in this patch -- using 'imm' directly, rather
> than insn[i].imm. I've still added your Tested-by since this shouldn't
> impact the fix in any way.
yep, it works nicely
thanks
jirka
>
> - Naveen
>
>
> 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 5cad5b5a7e9774..de8595880feec6 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -667,7 +667,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
> struct codegen_context *
> * 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 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
> struct codegen_context *
> 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);
> --
> 2.31.1
>
