diff mbox series

[bpf-next,3/7] powerpc: bpf: Fix off-by-one in tail call count limiting

Message ID 20210809093437.876558-4-johan.almbladh@anyfinetworks.com
State New
Headers show
Series Fix MAX_TAIL_CALL_CNT handling in eBPF JITs | expand

Commit Message

Johan Almbladh Aug. 9, 2021, 9:34 a.m. UTC 
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 mbox series

Patch

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++;