linux-kernel - [PATCH 4.13 03/53] MIPS: bpf: Fix uninitialised target compiler error

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Date:   Mon, 16 Oct 2017 18:16:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Matt Redfearn <matt.redfearn@...tec.com>,
        James Hogan <james.hogan@...tec.com>,
        David Daney <david.daney@...ium.com>,
        "David S. Miller" <davem@...emloft.net>,
        Colin Ian King <colin.king@...onical.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 4.13 03/53] MIPS: bpf: Fix uninitialised target compiler error

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

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

From: Matt Redfearn <matt.redfearn@...tec.com>

commit 94c3390ab84a6b449accc7351ffda4a0c17bdb92 upstream.

Compiling ebpf_jit.c with gcc 4.9 results in a (likely spurious)
compiler warning, as gcc has detected that the variable "target" may be
used uninitialised. Since -Werror is active, this is treated as an error
and causes a kernel build failure whenever CONFIG_MIPS_EBPF_JIT is
enabled.

arch/mips/net/ebpf_jit.c: In function 'build_one_insn':
arch/mips/net/ebpf_jit.c:1118:80: error: 'target' may be used
uninitialized in this function [-Werror=maybe-uninitialized]
    emit_instr(ctx, j, target);
                                                                                ^
cc1: all warnings being treated as errors

Fix this by initialising "target" to 0. If it really is used
uninitialised this would result in a jump to 0 and a detectable run time
failure.

Signed-off-by: Matt Redfearn <matt.redfearn@...tec.com>
Fixes: b6bd53f9c4e8 ("MIPS: Add missing file for eBPF JIT.")
Cc: James Hogan <james.hogan@...tec.com>
Cc: David Daney <david.daney@...ium.com>
Cc: David S. Miller <davem@...emloft.net>
Cc: Colin Ian King <colin.king@...onical.com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: linux-mips@...ux-mips.org
Cc: linux-kernel@...r.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17375/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/net/ebpf_jit.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/mips/net/ebpf_jit.c
+++ b/arch/mips/net/ebpf_jit.c
@@ -679,7 +679,7 @@ static int build_one_insn(const struct b
 {
 	int src, dst, r, td, ts, mem_off, b_off;
 	bool need_swap, did_move, cmp_eq;
-	unsigned int target;
+	unsigned int target = 0;
 	u64 t64;
 	s64 t64s;