[PATCH AUTOSEL 4.19 35/74] bpf: Fix off-by-one in tail call count limiting
From: Sasha Levin <sashal@kernel.org>
Date: 2021-09-09 13:40:02
Also in:
bpf, lkml, netdev
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
From: Johan Almbladh <johan.almbladh@anyfinetworks.com> [ Upstream commit b61a28cf11d61f512172e673b8f8c4a6c789b425 ] Before, the interpreter allowed up to MAX_TAIL_CALL_CNT + 1 tail calls. Now precisely MAX_TAIL_CALL_CNT is allowed, which is in line with the behavior of the x86 JITs. Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Yonghong Song <redacted> Link: https://lore.kernel.org/bpf/20210728164741.350370-1-johan.almbladh@anyfinetworks.com (local) Signed-off-by: Sasha Levin <sashal@kernel.org> --- kernel/bpf/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index d2b6d2459aad..b4a35c11bc92 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c@@ -1198,7 +1198,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) if (unlikely(index >= array->map.max_entries)) goto out; - if (unlikely(tail_call_cnt > MAX_TAIL_CALL_CNT)) + if (unlikely(tail_call_cnt >= MAX_TAIL_CALL_CNT)) goto out; tail_call_cnt++;
--
2.30.2