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

[Ben Hutchings]

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

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

From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: ast@xxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/13814/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 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;