[PATCH bpf-next 3/7] powerpc: bpf: Fix off-by-one in tail call count limiting
From: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Date: 2021-08-09 09:35:16
Also in:
bpf
Subsystem:
bpf jit for powerpc (32-bit and 64-bit), bpf [general] (safe dynamic programs and tools), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Hari Bathini, Christophe Leroy, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Madhavan Srinivasan, Linus Torvalds
Before, the eBPF JITs allowed up to MAX_TAIL_CALL_CNT + 1 tail calls. Now, precisely MAX_TAIL_CALL_CNT is allowed, which is in line with the behaviour of the interpreter. Verified with the test_bpf test suite on qemu-system-ppc and qemu-system-ppc64, respectively. Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com> --- arch/powerpc/net/bpf_jit_comp32.c | 4 ++-- arch/powerpc/net/bpf_jit_comp64.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index beb12cbc8c29..6d720728df09 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c@@ -221,13 +221,13 @@ static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 PPC_BCC(COND_GE, out); /* - * if (tail_call_cnt > MAX_TAIL_CALL_CNT) + * if (tail_call_cnt >= MAX_TAIL_CALL_CNT) * goto out; */ EMIT(PPC_RAW_CMPLWI(_R0, MAX_TAIL_CALL_CNT)); /* tail_call_cnt++; */ EMIT(PPC_RAW_ADDIC(_R0, _R0, 1)); - PPC_BCC(COND_GT, out); + PPC_BCC(COND_GE, out); /* prog = array->ptrs[index]; */ EMIT(PPC_RAW_RLWINM(_R3, b2p_index, 2, 0, 29));
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index b87a63dba9c8..2f4d24ed90a4 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c@@ -227,12 +227,12 @@ static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 PPC_BCC(COND_GE, out); /* - * if (tail_call_cnt > MAX_TAIL_CALL_CNT) + * if (tail_call_cnt >= MAX_TAIL_CALL_CNT) * goto out; */ PPC_BPF_LL(b2p[TMP_REG_1], 1, bpf_jit_stack_tailcallcnt(ctx)); EMIT(PPC_RAW_CMPLWI(b2p[TMP_REG_1], MAX_TAIL_CALL_CNT)); - PPC_BCC(COND_GT, out); + PPC_BCC(COND_GE, out); /* * tail_call_cnt++;
--
2.25.1