linux-kernel - [PATCH 3.16 101/346] bpf, mips: fix off-by-one in ctx offset allocation

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Message-ID: <lsq.1479082460.941175975@decadent.org.uk>
Date:   Mon, 14 Nov 2016 00:14:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Alexei Starovoitov" <ast@...nel.org>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        linux-mips@...ux-mips.org, "Ralf Baechle" <ralf@...ux-mips.org>,
        "Dan Carpenter" <dan.carpenter@...cle.com>
Subject: [PATCH 3.16 101/346] bpf, mips: fix off-by-one in ctx offset
 allocation

3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Daniel Borkmann <daniel@...earbox.net>

commit b4e76f7e6d3200462c6354a6ad4ae167459e61f8 upstream.

Dan Carpenter reported [1] a static checker warning that ctx->offsets[]
may be accessed off by one from build_body(), since it's allocated with
fp->len * sizeof(*ctx.offsets) as length. The cBPF arm and ppc code
doesn't have this issue as claimed, so only mips seems to be affected and
should like most other JITs allocate with fp->len + 1. A few number of
JITs (x86, sparc, arm64) handle this differently, where they only require
fp->len array elements.

  [1] http://www.spinics.net/lists/mips/msg64193.html

Fixes: c6610de353da ("MIPS: net: Add BPF JIT")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: ast@...nel.org
Cc: linux-mips@...ux-mips.org
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13814/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/mips/net/bpf_jit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -1365,7 +1365,7 @@ void bpf_jit_compile(struct sk_filter *f
 
 	memset(&ctx, 0, sizeof(ctx));
 
-	ctx.offsets = kcalloc(fp->len, sizeof(*ctx.offsets), GFP_KERNEL);
+	ctx.offsets = kcalloc(fp->len + 1, sizeof(*ctx.offsets), GFP_KERNEL);
 	if (ctx.offsets == NULL)
 		return;