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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.14 138/151] powerpc/bpf ppc32: Fix BPF_SUB when imm == 0x80000000
Date:   Mon, 11 Oct 2021 15:46:50 +0200
Message-Id: <20211011134522.263427461@linuxfoundation.org>
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From: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

[ Upstream commit 548b762763b885b81850db676258df47c55dd5f9 ]

Special case handling of the smallest 32-bit negative number for BPF_SUB.

Fixes: 51c66ad849a703 ("powerpc/bpf: Implement extended BPF on PPC32")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7135360a0cdf70adedbccf9863128b8daef18764.1633464148.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/net/bpf_jit_comp32.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index c48de048c8ce..a7759aa8043d 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -355,7 +355,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 				PPC_LI32(_R0, imm);
 				EMIT(PPC_RAW_ADDC(dst_reg, dst_reg, _R0));
 			}
-			if (imm >= 0)
+			if (imm >= 0 || (BPF_OP(code) == BPF_SUB && imm == 0x80000000))
 				EMIT(PPC_RAW_ADDZE(dst_reg_h, dst_reg_h));
 			else
 				EMIT(PPC_RAW_ADDME(dst_reg_h, dst_reg_h));
-- 
2.33.0