From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: davem@davemloft.net
Cc: daniel@iogearbox.net, andrii@kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH v2 bpf-next 1/3] bpf: Fix propagation of bounds from 64-bit min/max into 32-bit and var_off.
Date: Mon, 1 Nov 2021 15:21:51 -0700 [thread overview]
Message-ID: <20211101222153.78759-1-alexei.starovoitov@gmail.com> (raw)
From: Alexei Starovoitov <ast@kernel.org>
Before this fix:
166: (b5) if r2 <= 0x1 goto pc+22
from 166 to 189: R2=invP(id=1,umax_value=1,var_off=(0x0; 0xffffffff))
After this fix:
166: (b5) if r2 <= 0x1 goto pc+22
from 166 to 189: R2=invP(id=1,umax_value=1,var_off=(0x0; 0x1))
While processing BPF_JLE the reg_set_min_max() would set true_reg->umax_value = 1
and call __reg_combine_64_into_32(true_reg).
Without the fix it would not pass the condition:
if (__reg64_bound_u32(reg->umin_value) && __reg64_bound_u32(reg->umax_value))
since umin_value == 0 at this point.
Before commit 10bf4e83167c the umin was incorrectly ingored.
The commit 10bf4e83167c fixed the correctness issue, but pessimized
propagation of 64-bit min max into 32-bit min max and corresponding var_off.
Fixes: 10bf4e83167c ("bpf: Fix propagation of 32 bit unsigned bounds from 64 bit bounds")
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
kernel/bpf/verifier.c | 2 +-
tools/testing/selftests/bpf/verifier/array_access.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3c8aa7df1773..29671ed49ee8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1425,7 +1425,7 @@ static bool __reg64_bound_s32(s64 a)
static bool __reg64_bound_u32(u64 a)
{
- return a > U32_MIN && a < U32_MAX;
+ return a >= U32_MIN && a <= U32_MAX;
}
static void __reg_combine_64_into_32(struct bpf_reg_state *reg)
diff --git a/tools/testing/selftests/bpf/verifier/array_access.c b/tools/testing/selftests/bpf/verifier/array_access.c
index 1b1c798e9248..1b138cd2b187 100644
--- a/tools/testing/selftests/bpf/verifier/array_access.c
+++ b/tools/testing/selftests/bpf/verifier/array_access.c
@@ -186,7 +186,7 @@
},
.fixup_map_hash_48b = { 3 },
.errstr_unpriv = "R0 leaks addr",
- .errstr = "R0 unbounded memory access",
+ .errstr = "invalid access to map value, value_size=48 off=44 size=8",
.result_unpriv = REJECT,
.result = REJECT,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
--
2.30.2
next reply other threads:[~2021-11-01 22:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 22:21 Alexei Starovoitov [this message]
2021-11-01 22:21 ` [PATCH v2 bpf-next 2/3] bpf: Fix propagation of signed bounds from 64-bit min/max into 32-bit Alexei Starovoitov
2021-11-01 23:03 ` Yonghong Song
2021-11-01 23:06 ` Alexei Starovoitov
2021-11-01 23:11 ` Yonghong Song
2021-11-01 22:21 ` [PATCH v2 bpf-next 3/3] selftests/bpf: Add a testcase for 64-bit bounds propagation issue Alexei Starovoitov
2021-11-02 1:10 ` [PATCH v2 bpf-next 1/3] bpf: Fix propagation of bounds from 64-bit min/max into 32-bit and var_off patchwork-bot+netdevbpf
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