Re: [2.6.39-rc2, framebuffer] use after free oops

On 20 April 2011 17:56, Alan Cox [off-list ref] wrote:

On Wed, 20 Apr 2011 08:05:35 +0200
Bruno Prémont [off-list ref] wrote:

quoted

On Wed, 20 Apr 2011 13:50:10 Daniel J Blueman [off-list ref] wrote:

quoted

Any ideas on how best to address this issue [0], since it causes
silent corruption, or at best crashes?

There is probably no easy short-term fix to this...

The short term fix would be to deliberately leak the buffer. That should
go into 2.6.39-rc right now with a comment explaining the situation.
Otherwise who knows what corruption may occur to user data if unlucky.

The other 'cheat' might be to tweak the API so the removal API isn't a
'destroy' interface but a 'shut down' and has a matching 'restart' one
for when the intelfb unloads at which point vga16fb can carry on with the
original fb_info 8)

It looks like Andy Whitcroft addressed this issue some time ago, but
forgot to send the fix upstream:

http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-natty.git;a=patch;hÅa742b5f78e161d6a13853a7e3e6e1dfa429e69;hp&a1443f67eea17d4b78ef75df701782cc8bf35b

Let's hope it can hit -rc7 since it's been in Ubuntu's kernel tree for
considerable time, and fixes a silent corrupter:

http://groups.google.com/group/linux.kernel/browse_thread/thread/fc9083f6f380ed5b/f801112b840785cb?show_docidø01112b840785cb

Thanks,
  Daniel
-- 
Daniel J Blueman