On Fri, Feb 22, 2019 at 08:03:28AM -0800, Mark Salyzyn wrote: > From: "Arad, Ronen" <ronen.arad@xxxxxxxxx> > > Direct this upstream db65a3aaf29ecce2e34271d52e8d2336b97bd9fe sha to > stable 3.18. This patch addresses a race condition where a call to > > nlk->max_recvmsg_len = max(nlk->max_recvmsg_len, len); > nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len, > > one thread in-between another thread: > > skb = netlink_alloc_skb(sk, > > and > > skb_reserve(skb, skb_tailroom(skb) - > nlk->max_recvmsg_len); > > in netlink_dump. The result can be a negative value and will cause > a kernel panic ad BUG at net/core/skbuff.c because the negative value > turns into an extremely large positive value. > > Original commit: > > netlink_dump() allocates skb based on the calculated min_dump_alloc or > a per socket max_recvmsg_len. > min_alloc_size is maximum space required for any single netdev > attributes as calculated by rtnl_calcit(). > max_recvmsg_len tracks the user provided buffer to netlink_recvmsg. > It is capped at 16KiB. > The intention is to avoid small allocations and to minimize the number > of calls required to obtain dump information for all net devices. > > netlink_dump packs as many small messages as could fit within an skb > that was sized for the largest single netdev information. The actual > space available within an skb is larger than what is requested. It could > be much larger and up to near 2x with align to next power of 2 approach. > > Allowing netlink_dump to use all the space available within the > allocated skb increases the buffer size a user has to provide to avoid > truncaion (i.e. MSG_TRUNG flag set). > > It was observed that with many VLANs configured on at least one netdev, > a larger buffer of near 64KiB was necessary to avoid "Message truncated" > error in "ip link" or "bridge [-c[ompressvlans]] vlan show" when > min_alloc_size was only little over 32KiB. > > This patch trims skb to allocated size in order to allow the user to > avoid truncation with more reasonable buffer size. > > Signed-off-by: Ronen Arad <ronen.arad@xxxxxxxxx> > Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> > > (cherry pick commit db65a3aaf29ecce2e34271d52e8d2336b97bd9fe) > Signed-off-by: Mark Salyzyn <salyzyn@xxxxxxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Ronen Arad <ronen.arad@xxxxxxxxx> > Cc: "David S . Miller" <davem@xxxxxxxxxxxxx> > Cc: Dmitry Safonov <dima@xxxxxxxxxx> > Cc: David Ahern <dsahern@xxxxxxxxx> > Cc: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> > Cc: Andrei Vagin <avagin@xxxxxxxxxxxxx> > Cc: Li RongQing <lirongqing@xxxxxxxxx> > Cc: YU Bo <tsu.yubo@xxxxxxxxx> > Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> > Cc: netdev@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: stable@xxxxxxxxxxxxxxx # 3.18 > --- > net/netlink/af_netlink.c | 34 ++++++++++++++++++++++------------ > 1 file changed, 22 insertions(+), 12 deletions(-) Now queued up, thanks. greg k-h
