From: Albert Cahalan <albert@users.sf.net>
To: linux-kernel <linux-kernel@vger.kernel.org>
Cc: mitch@sfgoth.com
Subject: Re: Sound updating, security of strlcpy and a question on pci v unload
Date: 12 Jul 2003 10:03:17 -0400 [thread overview]
Message-ID: <1058018597.749.1317.camel@cube> (raw)
Mitchell Blank Jr writes:
> Mikulas Patocka wrote:
>> What's the difference there? strlcpy always creates null-terminated
>> string, strncpy doesn't. strncpy in kernel (unlike user strncpy) does not
>> pad the whole destination buffer with zeros (see comment and
>> implementation in lib/string.c), so I don't see any point why strncpy
>> should be more secure.
>
> Not only that, I think the point is usually moot anyway.
> If you're filling in a structure to pass to userspace like:
>
> struct whatever foo;
> strncpy(foo.name, "My Driver", sizeof(foo.name));
> foo.count = 1;
> [...]
>
> then you're STILL probably at risk of data leakage if "struct whatever"
> requires padding on any architecture. The real fix is to make sure
> that "foo" is explicitly zero'ed out first. Then strlcpy-vs-strncpy
> becomes a non-issue.
gcc -Wpadding ...
If the compiler has to add padding, then the programmer
most likely messed up. The warning catches stupidity.
Necessary padding can be explicit.
next reply other threads:[~2003-07-12 13:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-12 14:03 Albert Cahalan [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-07-11 17:05 Sound updating, security of strlcpy and a question on pci v unload Alan Cox
2003-07-11 19:04 ` Mikulas Patocka
2003-07-11 22:37 ` Mitchell Blank Jr
2003-07-12 0:08 ` Greg KH
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