mirror of
https://github.com/lkl/linux.git
synced 2025-12-19 08:03:01 +09:00
97550f6fa5
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.