This is a note to let you know that I've just added the patch titled batman-adv: Don't always reallocate the fragmentation skb head to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: batman-adv-don-t-always-reallocate-the-fragmentation-skb-head.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Tue Nov 23 01:39:02 PM CET 2021 From: Sven Eckelmann <sven@xxxxxxxxxxxxx> Date: Sat, 20 Nov 2021 13:39:38 +0100 Subject: batman-adv: Don't always reallocate the fragmentation skb head To: stable@xxxxxxxxxxxxxxx Cc: b.a.t.m.a.n@xxxxxxxxxxxxxxxxxxx, Sven Eckelmann <sven@xxxxxxxxxxxxx>, Simon Wunderlich <sw@xxxxxxxxxxxxxxxxxx> Message-ID: <20211120123939.260723-11-sven@xxxxxxxxxxxxx> From: Sven Eckelmann <sven@xxxxxxxxxxxxx> commit 992b03b88e36254e26e9a4977ab948683e21bd9f upstream. When a packet is fragmented by batman-adv, the original batman-adv header is not modified. Only a new fragmentation is inserted between the original one and the ethernet header. The code must therefore make sure that it has a writable region of this size in the skbuff head. But it is not useful to always reallocate the skbuff by this size even when there would be more than enough headroom still in the skb. The reallocation is just to costly during in this codepath. Fixes: ee75ed88879a ("batman-adv: Fragment and send skbs larger than mtu") Signed-off-by: Sven Eckelmann <sven@xxxxxxxxxxxxx> Signed-off-by: Simon Wunderlich <sw@xxxxxxxxxxxxxxxxxx> [ bp: 4.4 backported: adjust context, switch back to old return type + labels ] Signed-off-by: Sven Eckelmann <sven@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/batman-adv/fragmentation.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/net/batman-adv/fragmentation.c +++ b/net/batman-adv/fragmentation.c @@ -507,11 +507,13 @@ bool batadv_frag_send_packet(struct sk_b frag_header.no++; } - /* Make room for the fragment header. */ - if (batadv_skb_head_push(skb, header_size) < 0 || - pskb_expand_head(skb, header_size + ETH_HLEN, 0, GFP_ATOMIC) < 0) + /* make sure that there is at least enough head for the fragmentation + * and ethernet headers + */ + if (skb_cow_head(skb, ETH_HLEN + header_size) < 0) goto out_err; + skb_push(skb, header_size); memcpy(skb->data, &frag_header, header_size); /* Send the last fragment */ Patches currently in stable-queue which might be from sven@xxxxxxxxxxxxx are queue-4.4/batman-adv-consider-fragmentation-for-needed_headroom.patch queue-4.4/ath9k-fix-potential-interrupt-storm-on-queue-reset.patch queue-4.4/batman-adv-set-.owner-to-this_module.patch queue-4.4/batman-adv-mcast-fix-duplicate-mcast-packets-from-bla-backbone-to-mesh.patch queue-4.4/batman-adv-fix-multicast-tt-issues-with-bogus-roam-flags.patch queue-4.4/batman-adv-mcast-fix-duplicate-mcast-packets-in-bla-backbone-from-lan.patch queue-4.4/batman-adv-reserve-needed_-room-for-fragments.patch queue-4.4/net-batman-adv-fix-error-handling.patch queue-4.4/batman-adv-keep-fragments-equally-sized.patch queue-4.4/batman-adv-avoid-warn_on-timing-related-checks.patch queue-4.4/batman-adv-prevent-duplicated-softif_vlan-entry.patch queue-4.4/batman-adv-don-t-always-reallocate-the-fragmentation-skb-head.patch queue-4.4/batman-adv-mcast-fix-duplicate-mcast-packets-in-bla-backbone-from-mesh.patch