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| Filename | Latest commit message | Latest commit date |
|---|---|---|
c75c6e6e4f
[ Upstream commit 0e4427f8f587c4b603475468bb3aee9418574893 ]
After commit 22600596b675 ("ipv4: give an IPv4 dev to blackhole_netdev")
IPv4 neighbors can be constructed on the blackhole net device, but they
are constructed with an output function (neigh_direct_output()) that
simply calls dev_queue_xmit(). The latter will transmit packets via
'skb->dev' which might not be the blackhole net device if dst_dev_put()
switched 'dst->dev' to the blackhole net device while another CPU was
using the dst entry in ip_output(), but after it already initialized
'skb->dev' from 'dst->dev'.
Specifically, the following can happen:
CPU1 CPU2
udp_sendmsg(sk1) udp_sendmsg(sk2)
udp_send_skb() [...]
ip_output()
skb->dev = skb_dst(skb)->dev
dst_dev_put()
dst->dev = blackhole_netdev
ip_finish_output2()
resolves neigh on dst->dev
neigh_output()
neigh_direct_output()
dev_queue_xmit()
This will result in IPv4 packets being sent without an Ethernet header
via a valid net device:
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on enp9s0, link-type EN10MB (Ethernet), snapshot length 262144 bytes
22:07:02.329668 20:00:40:11:18:fb > 45:00:00:44:f4:94, ethertype Unknown
(0x58c6), length 68:
0x0000: 8dda 74ca f1ae ca6c ca6c 0098 969c 0400 ..t....l.l......
0x0010: 0000 4730 3f18 6800 0000 0000 0000 9971 ..G0?.h........q
0x0020: c4c9 9055 a157 0a70 9ead bf83 38ca ab38 ...U.W.p....8..8
0x0030: 8add ab96 e052 .....R
Fix by making sure that neighbors are constructed on top of the
blackhole net device with an output function that simply consumes the
packets, in a similar fashion to dst_discard_out() and
blackhole_netdev_xmit().
Fixes:
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.