From: David Miller <davem@davemloft.net>
To: nhorman@tuxdriver.com
Cc: David.Laight@ACULAB.COM, vyasevich@gmail.com,
netdev@vger.kernel.org, linux-sctp@vger.kernel.org
Subject: Re: [PATCH] sctp: Clean up type-punning in sctp_cmd_t union
Date: Mon, 29 Oct 2012 15:04:44 -0400 (EDT) [thread overview]
Message-ID: <20121029.150444.905377521761602639.davem@davemloft.net> (raw)
In-Reply-To: <20121029185932.GC10177@hmsreliant.think-freely.org>
From: Neil Horman <nhorman@tuxdriver.com>
Date: Mon, 29 Oct 2012 14:59:32 -0400
> I don't think thats whats going on at all. The problem, as commit
> 19c7e9eef503dc1ae926f3d26c56f88bee568d7b describes it, is that ia64 was
> speculatively loading a value from memory of type sctp_arg_t. If the
> initialization step set the value of one of the smaller members of the union
> (say a short), then the load stage may still load a larger amount of data (given
> that the union is larger than its smallest members). That results in part of
> the load being uninitalized, and ia64 declaring it Not A Thing, and consequently
> trapping out.
Agreed.
> The fix previously was to just initazlie the unsigned long member zero in that
> union before setting the actuall type member that was requried so as to ensure
> all the data was initalized. That works well enough, but it presumes that
> unsigned long is the largest member of the union, which is risky. Its better to
> memset the union to 0 for sizeof bytes to ensure future proofing.
Also agreed.
next prev parent reply other threads:[~2012-10-29 19:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-25 20:47 [PATCH] sctp: Clean up type-punning in sctp_cmd_t union Neil Horman
2012-10-25 21:42 ` Vlad Yasevich
2012-10-25 23:58 ` Neil Horman
2012-10-26 3:48 ` Vlad Yasevich
2012-10-26 13:24 ` Neil Horman
2012-10-26 19:12 ` Vlad Yasevich
2012-10-26 20:35 ` Neil Horman
2012-10-26 21:10 ` David Miller
2012-10-27 1:42 ` Neil Horman
2012-10-27 2:16 ` Vlad Yasevich
2012-10-29 15:07 ` David Laight
2012-10-29 18:59 ` Neil Horman
2012-10-29 19:04 ` David Miller [this message]
2012-10-26 9:00 ` David Laight
2012-10-26 13:28 ` Neil Horman
2012-10-26 13:41 ` [PATCH v2] " Neil Horman
2012-10-26 19:12 ` Vlad Yasevich
2012-10-29 16:35 ` Neil Horman
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