From: Ilya Leoshkevich <iii@linux.ibm.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: bpf@vger.kernel.org, Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Ilya Leoshkevich <iii@linux.ibm.com>
Subject: [PATCH bpf-next 01/11] bpf: Disable zero-extension for BPF_MEMSX
Date: Wed, 30 Aug 2023 03:07:42 +0200 [thread overview]
Message-ID: <20230830011128.1415752-2-iii@linux.ibm.com> (raw)
In-Reply-To: <20230830011128.1415752-1-iii@linux.ibm.com>
On the architectures that use bpf_jit_needs_zext(), e.g., s390x, the
verifier incorrectly inserts a zero-extension after BPF_MEMSX, leading
to miscompilations like the one below:
24: 89 1a ff fe 00 00 00 00 "r1 = *(s16 *)(r10 - 2);" # zext_dst set
0x3ff7fdb910e: lgh %r2,-2(%r13,%r0) # load halfword
0x3ff7fdb9114: llgfr %r2,%r2 # wrong!
25: 65 10 00 03 00 00 7f ff if r1 s> 32767 goto +3 <l0_1> # check_cond_jmp_op()
Disable such zero-extensions. The JITs need to insert sign-extension
themselves, if necessary.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
kernel/bpf/verifier.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index bb78212fa5b2..097985a46edc 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3110,7 +3110,9 @@ static void mark_insn_zext(struct bpf_verifier_env *env,
{
s32 def_idx = reg->subreg_def;
- if (def_idx == DEF_NOT_SUBREG)
+ if (def_idx == DEF_NOT_SUBREG ||
+ (BPF_CLASS(env->prog->insnsi[def_idx - 1].code) == BPF_LDX &&
+ BPF_MODE(env->prog->insnsi[def_idx - 1].code) == BPF_MEMSX))
return;
env->insn_aux_data[def_idx - 1].zext_dst = true;
--
2.41.0
next prev parent reply other threads:[~2023-08-30 1:11 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-30 1:07 [PATCH bpf-next 00/11] Implement cpuv4 support for s390x Ilya Leoshkevich
2023-08-30 1:07 ` Ilya Leoshkevich [this message]
2023-09-01 10:40 ` [PATCH bpf-next 01/11] bpf: Disable zero-extension for BPF_MEMSX Yonghong Song
2023-09-01 14:19 ` Puranjay Mohan
2023-09-01 14:56 ` Puranjay Mohan
2023-09-07 0:39 ` Alexei Starovoitov
2023-09-07 7:33 ` Puranjay Mohan
2023-09-07 15:36 ` Alexei Starovoitov
2023-09-07 16:39 ` Puranjay Mohan
2023-09-07 22:45 ` Alexei Starovoitov
2023-09-07 22:57 ` Puranjay Mohan
2023-09-12 22:49 ` Puranjay Mohan
2023-09-13 0:09 ` Alexei Starovoitov
2023-09-13 0:22 ` Puranjay Mohan
2023-09-13 1:49 ` Alexei Starovoitov
2023-09-13 6:10 ` Christophe Leroy
2023-09-03 8:16 ` Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 02/11] net: netfilter: Adjust timeouts of non-confirmed CTs in bpf_ct_insert_entry() Ilya Leoshkevich
2023-08-31 15:30 ` Daniel Borkmann
2023-09-03 8:23 ` Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 03/11] selftests/bpf: Unmount the cgroup2 work directory Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 04/11] selftests/bpf: Add big-endian support to the ldsx test Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 05/11] s390/bpf: Implement BPF_MOV | BPF_X with sign-extension Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 06/11] s390/bpf: Implement BPF_MEMSX Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 07/11] s390/bpf: Implement unconditional byte swap Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 08/11] s390/bpf: Implement unconditional jump with 32-bit offset Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 09/11] s390/bpf: Implement signed division Ilya Leoshkevich
2023-08-30 1:07 ` [PATCH bpf-next 10/11] selftests/bpf: Enable the cpuv4 tests for s390x Ilya Leoshkevich
2023-09-01 10:41 ` Yonghong Song
2023-08-30 1:07 ` [PATCH bpf-next 11/11] selftests/bpf: Trim DENYLIST.s390x Ilya Leoshkevich
2023-09-14 13:00 ` [PATCH bpf-next 00/11] Implement cpuv4 support for s390x patchwork-bot+netdevbpf
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