linux-kernel - Re: [Patch V2] crypto: x86/sha1 : Fix reads beyond the number of blocks passed

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Message-ID: <902d020b-5127-8611-9656-bf0062d1e09b@redhat.com>
Date:   Wed, 2 Aug 2017 12:39:53 +0200
From:   Jan Stancek <jstancek@...hat.com>
To:     Megha Dey <megha.dey@...ux.intel.com>, herbert@...dor.apana.org.au
Cc:     tim.c.chen@...ux.intel.com, davem@...emloft.net,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        ilya.albrekht@...el.com, megha.dey@...el.com, jstancek@...hat.com
Subject: Re: [Patch V2] crypto: x86/sha1 : Fix reads beyond the number of
 blocks passed

On 08/02/2017 02:38 AM, Megha Dey wrote:
> It was reported that the sha1 AVX2 function(sha1_transform_avx2) is
> reading ahead beyond its intended data, and causing a crash if the next
> block is beyond page boundary:
> http://marc.info/?l=linux-crypto-vger&m=149373371023377
> 
> This patch makes sure that there is no overflow for any buffer length.
> 
> It passes the tests written by Jan Stancek that revealed this problem:
> https://github.com/jstancek/sha1-avx2-crash
> 
> Jan, can you verify this fix?

Hi,

Looks good, my tests (below) PASS-ed.

I updated reproducer at [1] to try more than just single scenario. It
now tries thousands of combinations with different starting offset within
page and sizes of data chunks.

(without patch) v4.13-rc3-102-g26c5ceb with avx2 enabled:
[  106.455175] sha_test module loaded
[  106.460458] data is at 0xffff8c88e58f8000, page_after_data: 0xffff8c88e58fa000
[  106.468625] sha_test testing hash: sha1-generic, maxlen: 8192
[  127.091237] sha_test hash: sha1-generic calculated 1764032 hashes
[  127.098038] sha_test testing hash: sha1-ni, maxlen: 8192
[  127.108805] failed to alloc sha1-ni
[  127.112703] sha_test testing hash: sha1-avx, maxlen: 8192
[  141.166611] sha_test hash: sha1-avx calculated 1764032 hashes
[  141.173023] sha_test testing hash: sha1-avx2, maxlen: 8192
[  141.180046] BUG: unable to handle kernel paging request at ffff8c88e58fa000
[  141.187817] IP: _begin+0x28/0x187
[  141.191512] PGD 89c578067
[  141.191513] P4D 89c578067
[  141.194529] PUD c61f0a063
[  141.197545] PMD c64cb1063
[  141.200561] PTE 8000000c658fa062
[  141.203577]
[  141.208832] Oops: 0000 [#1] SMP
...

With patch "[Patch V2] crypto: x86/sha1 : Fix reads beyond the number of blocks passed":
[  406.323781] sha_test module loaded
[  406.329062] data is at 0xffff93ab97108000, page_after_data: 0xffff93ab9710a000
[  406.337185] sha_test testing hash: sha1-generic, maxlen: 8192
[  426.157242] sha_test hash: sha1-generic calculated 1764032 hashes
[  426.164043] sha_test testing hash: sha1-ni, maxlen: 8192
[  426.174244] failed to alloc sha1-ni
[  426.178139] sha_test testing hash: sha1-avx, maxlen: 8192
[  440.226240] sha_test hash: sha1-avx calculated 1764032 hashes
[  440.232651] sha_test testing hash: sha1-avx2, maxlen: 8192
[  452.497988] sha_test hash: sha1-avx2 calculated 1764032 hashes
[  452.504495] sha_test testing hash: sha1-ssse3, maxlen: 8192
[  467.319316] sha_test hash: sha1-ssse3 calculated 1764032 hashes
[  467.325922] sha_test done
[  471.827083] sha_test module unloaded

I also ran a test at [2], which is comparing hashes produced by
kernel with hashes produced by user-space utilities (e.g. 'sha1sum').
This test also PASS-ed.

Regards,
Jan

[1] https://github.com/jstancek/sha1-avx2-crash
[2] https://github.com/jstancek/kernel_sha_test/tree/sha1-avx2-4.13

> Herbert, can you re-enable sha1-avx2 once Jan has checked it out and
> revert commit b82ce24426a4071da9529d726057e4e642948667 ?
> 
> Originally-by: Ilya Albrekht <ilya.albrekht@...el.com>
> Signed-off-by: Megha Dey <megha.dey@...ux.intel.com>
> Reported-by: Jan Stancek <jstancek@...hat.com>