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| author | Willem de Bruijn <willemb@google.com> | 2021-01-09 23:18:33 +0100 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2021-01-12 03:20:09 +0100 |
| commit | 97550f6fa59254435d864b92603de3ca4b5a99f8 (patch) | |
| tree | a2236300b4b899a2e4a34e73dffe85910f455faa /include | |
| parent | net: support kmap_local forced debugging in skb_frag_foreach (diff) | |
| download | linux-97550f6fa59254435d864b92603de3ca4b5a99f8.tar.xz linux-97550f6fa59254435d864b92603de3ca4b5a99f8.zip | |
net: compound page support in skb_seq_read
skb_seq_read iterates over an skb, returning pointer and length of
the next data range with each call.
It relies on kmap_atomic to access highmem pages when needed.
An skb frag may be backed by a compound page, but kmap_atomic maps
only a single page. There are not enough kmap slots to always map all
pages concurrently.
Instead, if kmap_atomic is needed, iterate over each page.
As this increases the number of calls, avoid this unless needed.
The necessary condition is captured in skb_frag_must_loop.
I tried to make the change as obvious as possible. It should be easy
to verify that nothing changes if skb_frag_must_loop returns false.
Tested:
On an x86 platform with
CONFIG_HIGHMEM=y
CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP=y
CONFIG_NETFILTER_XT_MATCH_STRING=y
Run
ip link set dev lo mtu 1500
iptables -A OUTPUT -m string --string 'badstring' -algo bm -j ACCEPT
dd if=/dev/urandom of=in bs=1M count=20
nc -l -p 8000 > /dev/null &
nc -w 1 -q 0 localhost 8000 < in
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/skbuff.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index c858adfb5a82..5f60c9e907c9 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1203,6 +1203,7 @@ struct skb_seq_state { struct sk_buff *root_skb; struct sk_buff *cur_skb; __u8 *frag_data; + __u32 frag_off; }; void skb_prepare_seq_read(struct sk_buff *skb, unsigned int from, |