Re: [PATCH AUTOSEL 5.14 101/252] bpf: Fix off-by-one in tail call count limiting
From: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Date: 2021-09-14 04:09:14
Also in:
bpf, lkml, stable
Sasha,
This patch should not be applied to any of the stable kernels. It was
reverted in f9dabe016b63 ("bpf: Undo off-by-one in interpreter tail
call count limit").
I don't think it will pass the CI selftests so maybe it wouldn't be
applied anyway, but nevertheless I want to inform you about it.
Johan
On Thu, Sep 9, 2021 at 1:43 PM Sasha Levin [off-list ref] wrote:quoted hunk ↗ jump to hunk
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 0a28a8095d3e..82af6279992d 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c@@ -1564,7 +1564,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn) 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