linux-kernel - [PATCH 3.19.y-ckt 043/146] arm64: bpf: fix signedness bug in loading 64-bit immediate

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Message-Id: <1434579851-1719-44-git-send-email-kamal@canonical.com>
Date:	Wed, 17 Jun 2015 15:22:28 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Zi Shen Lim <zlim.lnx@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Xi Wang <xi.wang@...il.com>, Will Deacon <will.deacon@....com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 043/146] arm64: bpf: fix signedness bug in loading 64-bit immediate

3.19.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xi Wang <xi.wang@...il.com>

commit 1e4df6b7208140f3c49f316d33a409d3a161f350 upstream.

Consider "(u64)insn1.imm << 32 | imm" in the arm64 JIT.  Since imm is
signed 32-bit, it is sign-extended to 64-bit, losing the high 32 bits.
The fix is to convert imm to u32 first, which will be zero-extended to
u64 implicitly.

Cc: Zi Shen Lim <zlim.lnx@...il.com>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Catalin Marinas <catalin.marinas@....com>
Fixes: 30d3d94cc3d5 ("arm64: bpf: add 'load 64-bit immediate' instruction")
Signed-off-by: Xi Wang <xi.wang@...il.com>
[will: removed non-arm64 bits and redundant casting]
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/arm64/net/bpf_jit_comp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index edba042..dc6a484 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -487,7 +487,7 @@ emit_cond_jmp:
 			return -EINVAL;
 		}
 
-		imm64 = (u64)insn1.imm << 32 | imm;
+		imm64 = (u64)insn1.imm << 32 | (u32)imm;
 		emit_a64_mov_i64(dst, imm64, ctx);
 
 		return 1;
-- 
1.9.1

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