Re: [B.A.T.M.A.N.] [PATCHv4 maint 5/5] batman-adv: Fix potential synchronization issues in mcast tvlv handler

[Marek Lindner <mareklindner@neomailbox.ch>]

[-- Attachment #1: Type: text/plain, Size: 1460 bytes --]

On Tuesday, June 16, 2015 17:10:26 Linus Lüssing wrote:
> So far the mcast tvlv handler did not anticipate the processing of
> multiple incoming OGMs from the same originator at the same time. This
> can lead to various issues:
> 
> * Broken refcounting: For instance two mcast handlers might both assume
>   that an originator just got multicast capabilities and will together
>   wrongly decrease mcast.num_disabled by two, potentially leading to
>   an integer underflow.
> 
> * Potential kernel panic on hlist_del_rcu(): Two mcast handlers might
>   one after another try to do an
>   hlist_del_rcu(&orig->mcast_want_all_*_node). The second one will
>   cause memory corruption / crashes.
>   (Reported by: Sven Eckelmann <sven@narfation.org>)
> 
> Right in the beginning the code path makes assumptions about the current
> multicast related state of an originator and bases all updates on that. The
> easiest and least error prune way to fix the issues in this case is to
> serialize multiple mcast handler invocations with a spinlock.
> 
> Fixes: 77ec494490d6 ("batman-adv: Announce new capability via multicast
> TVLV") Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
> ---
>  multicast.c  |   62
> ++++++++++++++++++++++++++++++++++++++++++++++------------ originator.c
> |    4 ++++
>  types.h      |    3 +++
>  3 files changed, 56 insertions(+), 13 deletions(-)

Applied in revision 7f220ed.

Thanks,
Marek

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 473 bytes --]