From ef17af2a817db97d42dd2ec0a425231748e23dbc Mon Sep 17 00:00:00 2001
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Date: Fri, 5 Dec 2014 16:40:07 +0100
Subject: [PATCH] fs: nfsd: Fix signedness bug in compare_blob

Bugs similar to the one in acbbe6fbb240 (kcmp: fix standard comparison
bug) are in rich supply.

In this variant, the problem is that struct xdr_netobj::len has type
unsigned int, so the expression o1->len - o2->len _also_ has type
unsigned int; it has completely well-defined semantics, and the result
is some non-negative integer, which is always representable in a long
long. But this means that if the conditional triggers, we are
guaranteed to return a positive value from compare_blob.

In this case it could be fixed by

-       res = o1->len - o2->len;
+       res = (long long)o1->len - (long long)o2->len;

but I'd rather eliminate the usually broken 'return a - b;' idiom.

Reviewed-by: Jeff Layton <jlayton@primarydata.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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