Messages in this thread | | | From | Roberto Sassu <> | Subject | RE: [PATCH v2 3/6] ima: Fix ima digest hash table key calculation | Date | Tue, 28 Apr 2020 07:19:59 +0000 |
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> -----Original Message----- > From: David Laight [mailto:David.Laight@ACULAB.COM] > Sent: Monday, April 27, 2020 4:28 PM > To: Roberto Sassu <roberto.sassu@huawei.com>; zohar@linux.ibm.com; > rgoldwyn@suse.de > Cc: linux-integrity@vger.kernel.org; linux-security-module@vger.kernel.org; > linux-kernel@vger.kernel.org; Silviu Vlasceanu > <Silviu.Vlasceanu@huawei.com>; Krzysztof Struczynski > <krzysztof.struczynski@huawei.com>; stable@vger.kernel.org > Subject: RE: [PATCH v2 3/6] ima: Fix ima digest hash table key calculation > > From: Roberto Sassu > > Sent: 27 April 2020 13:51 > ... > > > > -static inline unsigned long ima_hash_key(u8 *digest) > > > > +static inline unsigned int ima_hash_key(u8 *digest) > > > > { > > > > - return hash_long(*digest, IMA_HASH_BITS); > > > > + return (*(unsigned int *)digest % IMA_MEASURE_HTABLE_SIZE); > > > > > > That almost certainly isn't right. > > > It falls foul of the *(integer_type *)ptr being almost always wrong. > > > > I didn't find the problem. Can you please explain? > > The general problem with *(int_type *)ptr is that it does completely > the wrong thing if 'ptr' is the address of a larger integer type on > a big-endian system. > You may also get a misaligned access trap. > > In this case I guess that digest is actually u8[SHA1_DIGEST_SIZE]. > Maybe what you should return is: > (digest[0] | digest[1] << 8) % IMA_MEASURE_HTABLE_SIZE; > and comment that there is no point taking a hash of part of > a SHA1 digest.
Ok, thanks.
Roberto
HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli
> David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, > MK1 1PT, UK > Registration No: 1397386 (Wales)
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