netdev - [PATCH v2 bpf-next 2/3] bpf: Fix propagation of signed bounds from 64-bit min/max into 32-bit.

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Date:   Mon,  1 Nov 2021 15:21:52 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     davem@...emloft.net
Cc:     daniel@...earbox.net, andrii@...nel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, kernel-team@...com
Subject: [PATCH v2 bpf-next 2/3] bpf: Fix propagation of signed bounds from 64-bit min/max into 32-bit.

From: Alexei Starovoitov <ast@...nel.org>

Similar to unsigned bounds propagation fix signed bounds.
The 'Fixes' tag is a hint. There is no security bug here.
The verifier was too conservative.

Fixes: 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking")
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 29671ed49ee8..a4b48bd4e3ca 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1420,7 +1420,7 @@ static void __reg_combine_32_into_64(struct bpf_reg_state *reg)
 
 static bool __reg64_bound_s32(s64 a)
 {
-	return a > S32_MIN && a < S32_MAX;
+	return a >= S32_MIN && a <= S32_MAX;
 }
 
 static bool __reg64_bound_u32(u64 a)
-- 
2.30.2