This is a note to let you know that I've just added the patch titled
skbuff: orphan frags before zerocopy clone
to the 4.14-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:
skbuff-orphan-frags-before-zerocopy-clone.patch
and it can be found in the queue-4.14 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 Sun Dec 31 11:12:48 CET 2017
From: Willem de Bruijn <willemb@xxxxxxxxxx>
Date: Wed, 20 Dec 2017 17:37:49 -0500
Subject: skbuff: orphan frags before zerocopy clone
From: Willem de Bruijn <willemb@xxxxxxxxxx>
[ Upstream commit 268b790679422a89e9ab0685d9f291edae780c98 ]
Call skb_zerocopy_clone after skb_orphan_frags, to avoid duplicate
calls to skb_uarg(skb)->callback for the same data.
skb_zerocopy_clone associates skb_shinfo(skb)->uarg from frag_skb
with each segment. This is only safe for uargs that do refcounting,
which is those that pass skb_orphan_frags without dropping their
shared frags. For others, skb_orphan_frags drops the user frags and
sets the uarg to NULL, after which sock_zerocopy_clone has no effect.
Qemu hangs were reported due to duplicate vhost_net_zerocopy_callback
calls for the same data causing the vhost_net_ubuf_ref_>refcount to
drop below zero.
Link: http://lkml.kernel.org/r/<CAF=yD-LWyCD4Y0aJ9O0e_CHLR+3JOeKicRRTEVCPxgw4XOcqGQ@xxxxxxxxxxxxxx>
Fixes: 1f8b977ab32d ("sock: enable MSG_ZEROCOPY")
Reported-by: Andreas Hartmann <andihartmann@xxxxxxxxxxxxxxx>
Reported-by: David Hill <dhill@xxxxxxxxxx>
Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/core/skbuff.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3657,8 +3657,6 @@ normal:
skb_shinfo(nskb)->tx_flags |= skb_shinfo(head_skb)->tx_flags &
SKBTX_SHARED_FRAG;
- if (skb_zerocopy_clone(nskb, head_skb, GFP_ATOMIC))
- goto err;
while (pos < offset + len) {
if (i >= nfrags) {
@@ -3684,6 +3682,8 @@ normal:
if (unlikely(skb_orphan_frags(frag_skb, GFP_ATOMIC)))
goto err;
+ if (skb_zerocopy_clone(nskb, frag_skb, GFP_ATOMIC))
+ goto err;
*nskb_frag = *frag;
__skb_frag_ref(nskb_frag);
Patches currently in stable-queue which might be from willemb@xxxxxxxxxx are
queue-4.14/skbuff-skb_copy_ubufs-must-release-uarg-even-without-user-frags.patch
queue-4.14/sock-free-skb-in-skb_complete_tx_timestamp-on-error.patch
queue-4.14/skbuff-orphan-frags-before-zerocopy-clone.patch
queue-4.14/skbuff-in-skb_copy_ubufs-unclone-before-releasing-zerocopy.patch