Re: [PATCH] bpf: Fix off-by-one in tail call count limiting
From: Yonghong Song <hidden>
Date: 2021-07-28 19:13:36
Also in:
bpf
On 7/28/21 9:47 AM, Johan Almbladh wrote:
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>
LGTM.
Acked-by: Yonghong Song <redacted>
I also checked arm/arm64 jit. I saw the following comments:
/* if (tail_call_cnt > MAX_TAIL_CALL_CNT)
* goto out;
* tail_call_cnt++;
*/
Maybe we have this MAX_TAIL_CALL_CNT + 1 issue
for arm/arm64 jit?
quoted hunk ↗ jump to hunk
--- 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 9b1577498373..67682b3afc84 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c@@ -1559,7 +1559,7 @@ 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++;