From: Johan Almbladh <johan.almbladh@anyfinetworks.com>
To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org
Cc: kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
john.fastabend@gmail.com, kpsingh@kernel.org,
netdev@vger.kernel.org, bpf@vger.kernel.org,
illusionist.neo@gmail.com, zlim.lnx@gmail.com,
paulburton@kernel.org, naveen.n.rao@linux.ibm.com,
sandipan@linux.ibm.com, luke.r.nels@gmail.com, bjorn@kernel.org,
iii@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com,
davem@davemloft.net, udknight@gmail.com,
Johan Almbladh <johan.almbladh@anyfinetworks.com>
Subject: [PATCH bpf-next 1/7] arm: bpf: Fix off-by-one in tail call count limiting
Date: Mon, 9 Aug 2021 11:34:31 +0200 [thread overview]
Message-ID: <20210809093437.876558-2-johan.almbladh@anyfinetworks.com> (raw)
In-Reply-To: <20210809093437.876558-1-johan.almbladh@anyfinetworks.com>
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-arm.
Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
---
arch/arm/net/bpf_jit_32.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index a951276f0547..200ae9d24205 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -1180,12 +1180,12 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
/* tmp2[0] = array, tmp2[1] = index */
- /* if (tail_call_cnt > MAX_TAIL_CALL_CNT)
+ /* if (tail_call_cnt >= MAX_TAIL_CALL_CNT)
* goto out;
* tail_call_cnt++;
*/
- lo = (u32)MAX_TAIL_CALL_CNT;
- hi = (u32)((u64)MAX_TAIL_CALL_CNT >> 32);
+ lo = (u32)(MAX_TAIL_CALL_CNT - 1);
+ hi = (u32)((u64)(MAX_TAIL_CALL_CNT - 1) >> 32);
tc = arm_bpf_get_reg64(tcc, tmp, ctx);
emit(ARM_CMP_I(tc[0], hi), ctx);
_emit(ARM_COND_EQ, ARM_CMP_I(tc[1], lo), ctx);
--
2.25.1
next prev parent reply other threads:[~2021-08-09 9:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-09 9:34 [PATCH bpf-next 0/7] Fix MAX_TAIL_CALL_CNT handling in eBPF JITs Johan Almbladh
2021-08-09 9:34 ` Johan Almbladh [this message]
2021-08-09 9:34 ` [PATCH bpf-next 2/7] arm64: bpf: Fix off-by-one in tail call count limiting Johan Almbladh
2021-08-09 9:34 ` [PATCH bpf-next 3/7] powerpc: " Johan Almbladh
2021-08-09 9:34 ` [PATCH bpf-next 4/7] s390: " Johan Almbladh
2021-08-09 12:24 ` Ilya Leoshkevich
2021-08-09 21:09 ` Johan Almbladh
2021-08-09 9:34 ` [PATCH bpf-next 5/7] sparc: " Johan Almbladh
2021-08-09 9:34 ` [PATCH bpf-next 6/7] mips: " Johan Almbladh
2021-08-09 9:34 ` [PATCH bpf-next 7/7] x86: bpf: Fix comments on " Johan Almbladh
2021-08-09 15:41 ` Daniel Borkmann
2021-08-09 18:02 ` Johan Almbladh
2021-08-12 16:36 ` [PATCH bpf-next 0/7] Fix MAX_TAIL_CALL_CNT handling in eBPF JITs Paul Chaignon
2021-08-16 7:17 ` Johan Almbladh
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