[PATCH bpf-next 4/7] s390: bpf: Fix off-by-one in tail call count limiting
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STALE1894d
From: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Date: 2021-08-09 09:35:21
Also in:
bpf
Subsystem:
bpf jit for s390, bpf [general] (safe dynamic programs and tools), s390 architecture, the rest · Maintainers:
Ilya Leoshkevich, Heiko Carstens, Vasily Gorbik, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Alexander Gordeev, Linus Torvalds
Before, the eBPF JIT 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-s390x. Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com> --- arch/s390/net/bpf_jit_comp.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 88419263a89a..f6cdf13285ed 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c@@ -1363,7 +1363,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, jit->prg); /* - * if (tail_call_cnt++ > MAX_TAIL_CALL_CNT) + * if (tail_call_cnt++ >= MAX_TAIL_CALL_CNT) * goto out; */
@@ -1377,8 +1377,8 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, EMIT6_DISP_LH(0xeb000000, 0x00fa, REG_W1, REG_W0, REG_15, off); /* clij %w1,MAX_TAIL_CALL_CNT,0x2,out */ patch_2_clij = jit->prg; - EMIT6_PCREL_RIEC(0xec000000, 0x007f, REG_W1, MAX_TAIL_CALL_CNT, - 2, jit->prg); + EMIT6_PCREL_RIEC(0xec000000, 0x007f, REG_W1, + MAX_TAIL_CALL_CNT - 1, 2, jit->prg); /* * prog = array->ptrs[index];
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2.25.1