From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vyacheslav Dubeyko Subject: Re: [PATCH] fs: hfs: Fix comparison bug in hfs_cat_keycmp Date: Wed, 10 Dec 2014 11:23:27 -0800 Message-ID: <1418239407.2963.1.camel@ubuntu> References: <1418165449.5917.4.camel@ubuntu> <1418229164-4132-1-git-send-email-linux@rasmusvillemoes.dk> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Rasmus Villemoes Return-path: In-Reply-To: <1418229164-4132-1-git-send-email-linux@rasmusvillemoes.dk> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, 2014-12-10 at 17:32 +0100, Rasmus Villemoes wrote: > Relying on the sign (after casting to int) of the difference of two > quantities for comparison is usually wrong. For example, should a-b > turn out to be 2^31, the return value of cmp(a,b) is -2^31; but that > would also be the return value from cmp(b, a). So a compares less than > b and b compares less than a. One can also easily find three values > a,b,c such that a compares less than b, b compares less than c, but a > does not compare less than c. > Looks good for me. Thank you for the fix. Reviewed-by: Vyacheslav Dubeyko Thanks, Vyacheslav Dubeyko. > Signed-off-by: Rasmus Villemoes > --- > fs/hfs/catalog.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/fs/hfs/catalog.c b/fs/hfs/catalog.c > index ff0316b925a5..db458ee3a546 100644 > --- a/fs/hfs/catalog.c > +++ b/fs/hfs/catalog.c > @@ -162,14 +162,16 @@ err2: > */ > int hfs_cat_keycmp(const btree_key *key1, const btree_key *key2) > { > - int retval; > + __be32 k1p, k2p; > > - retval = be32_to_cpu(key1->cat.ParID) - be32_to_cpu(key2->cat.ParID); > - if (!retval) > - retval = hfs_strcmp(key1->cat.CName.name, key1->cat.CName.len, > - key2->cat.CName.name, key2->cat.CName.len); > + k1p = key1->cat.ParID; > + k2p = key2->cat.ParID; > > - return retval; > + if (k1p != k2p) > + return be32_to_cpu(k1p) < be32_to_cpu(k2p) ? -1 : 1; > + > + return hfs_strcmp(key1->cat.CName.name, key1->cat.CName.len, > + key2->cat.CName.name, key2->cat.CName.len); > } > > /* Try to get a catalog entry for given catalog id */