APPLIED(B): [SRU][Bionic/Cosmic/Unstable][PATCH 0/1] Fix regression in 'ip --family bridge neigh' since Linux v4.12

[Khaled Elmously]

On 2018-10-08 17:07:28 , Mauricio Faria de Oliveira wrote:
> BugLink: https://bugs.launchpad.net/bugs/1796748
> 
> [Impact]
> 
>  * Netlink RTM_GETNEIGH requests for PF_BRIDGE are broken since linux  v4.12.
> 
>  * Users, tools (e.g., iproute2), and libraries (e.g., go netlink) that use
>    such request/family currently receive nothing back in the kernel response.
> 
>  * The upstream fix resolves the breakage in the userspace-kernel interface
>    by explicitly checking for the old/broken request to ensure it's replied.
> 
> [Test Case]
> 
>  * The command 'ip --family bridge neigh' returns nothing on broken kernels,
>    and matches 'bridge fdb show' on fixed kernels.
> 
>  * Before:
> 
>     $ ip --family bridge neigh
>     $
> 
>  * After:
> 
>     $ ip --family bridge neigh
>     dev ens3 lladdr 33:33:00:00:00:01 PERMANENT
>     dev ens3 lladdr 01:00:5e:00:00:01 PERMANENT
>     dev ens3 lladdr 33:33:ff:e9:9d:60 PERMANENT
> 
>  * Reference:
> 
>     $ bridge fdb show
>     33:33:00:00:00:01 dev ens3 self permanent
>     01:00:5e:00:00:01 dev ens3 self permanent
>     33:33:ff:e9:9d:60 dev ens3 self permanent
> 
> [Regression Potential]
> 
>  * Low, for three reasons:
> 
>  * The fix is fairly contained (RTM_GETNEIGH request for PF_BRIDGE family).
> 
>  * The checks introduced by the fix are conservative, based on the size
>    of the old request (the size of the old/new requests are different),
>    and it does nothing different in case the (old) size doesn't match.
> 
>  * Given the above, only applications with message length and contents
>    specially hand-crafted (and likely not valid nor useful) might fail.
>    To the best of my knowledge, this is not the common case out there.
> 
> [Other Info]
> 
>  * The patch is only applicable to v4.12+ (so not Trusty nor Xenial).
> 
>  * The patch is the same for Bionic, Cosmic, and unstable.
> 
>  * Upstream commit: bd961c9bc664 ("rtnetlink: fix rtnl_fdb_dump() for
>    ndmsg header")
>    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bd961c9bc66497f0c63f4ba1d02900bb85078366
> 
> Mauricio Faria de Oliveira (1):
>   rtnetlink: fix rtnl_fdb_dump() for ndmsg header
> 
>  net/core/rtnetlink.c | 29 ++++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 9 deletions(-)
> 
> -- 
> 2.17.1
> 
> 
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