lkml.org 
[lkml]   [2011]   [Oct]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: PROBLEM: System call 'sendmsg' of process ospfd (quagga) causes kernel oops
From
Date
Le mardi 18 octobre 2011 à 11:34 +0200, Herbert Xu a écrit :
> On Tue, Oct 18, 2011 at 04:30:32AM +0200, Eric Dumazet wrote:
> >
> > If David/Herbert/Timo agree, then patch should find its way into current
> > kernel, then to stable trees as well.
>
> Actually, I think we should instead fix the users of needed_headroom
> to not read it twice which is causing problems here.
>
> GRE tunnels by their nature do not have a fixed value for
> needed_headroom. As the underlying routes change the necessary
> headroom may need to be adjusted due to further encapsulation such
> as IPsec.
>
> Keeping it constant from tunnel creation may result in suboptimal
> performance due to unnecessary header reallocations.
>
> However, until we audit the stack to see if there are further
> instances of double-readings such as the one causing the crash
> here, I'm fine with your patch making it constant.
>
> Once we're sure that all of the double-readings are gone we
> can revert to a dynamic needed_headroom.
>

Sure, we can work on this path for future kernels.

Adding an RCU protected structure to hold hard_header_len /
needed_headroom / needed_tailroom should be possible, but this adds yet
another pointer dereference...

Thanks !


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

\
 
 \ /
  Last update: 2011-10-18 12:03    [W:0.153 / U:0.544 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site