linux-kernel - Re: [PATCH v5 16/18] perf: enable reading of perf.data files from different ABI rev

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4F315430.2090708@gmail.com>
Date:	Tue, 07 Feb 2012 09:41:20 -0700
From:	David Ahern <dsahern@...il.com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	acme@...hat.com, robert.richter@....com, ming.m.lin@...el.com,
	andi@...stfloor.org, asharma@...com, ravitillo@....gov,
	vweaver1@...s.utk.edu, khandual@...ux.vnet.ibm.com
Subject: Re: [PATCH v5 16/18] perf: enable reading of perf.data files from
 different ABI rev

On 02/07/2012 08:50 AM, Stephane Eranian wrote:
>>> +     if (sz == 0) {
>>> +             /* assume ABI0 */
>>> +             sz =  PERF_ATTR_SIZE_VER0;
>>
>> Shouldn't this be a failure? ie., problem with the file (or the
>> swapping) since size can't be 0
>>
> size can be zero. In which case, it means ABI0 version.
> See kernel/event/core.c:perf_copy_attr().

ok

> 
> 
>> And then for the following why not restrict sz to known, expected sizes
>> -- using the PERF_ATTR_SIZE_VER defines introduced in patch 15?
>>
> Well, the current code solves the problem once and for all. Old tools
> can still read new files and vice-versa. If you think that's a problem I
> can simply bail out if sz > our_sz.

My sensitivity on this is when endianness is broken it is a nightmare to
find. You end up lacing the code with printfs trying to find which size
field is going off the charts making the parsing of the file fail - or
worse the sizes are slightly off and you get non-sense out.

New commands should be able to read old files; old commands reading new
files is a bit of a stretch in that the code has to be future-proofed.
It seems like a reasonable requirement for data files to be examined by
a command of the same vintage or newer as the command that wrote the file.

David
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/