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Sheng Lan 5845f70638 net: netem: fix skb length BUG_ON in __skb_to_sgvec
It can be reproduced by following steps:
1. virtio_net NIC is configured with gso/tso on
2. configure nginx as http server with an index file bigger than 1M bytes
3. use tc netem to produce duplicate packets and delay:
   tc qdisc add dev eth0 root netem delay 100ms 10ms 30% duplicate 90%
4. continually curl the nginx http server to get index file on client
5. BUG_ON is seen quickly

[10258690.371129] kernel BUG at net/core/skbuff.c:4028!
[10258690.371748] invalid opcode: 0000 [#1] SMP PTI
[10258690.372094] CPU: 5 PID: 0 Comm: swapper/5 Tainted: G        W         5.0.0-rc6 #2
[10258690.372094] RSP: 0018:ffffa05797b43da0 EFLAGS: 00010202
[10258690.372094] RBP: 00000000000005ea R08: 0000000000000000 R09: 00000000000005ea
[10258690.372094] R10: ffffa0579334d800 R11: 00000000000002c0 R12: 0000000000000002
[10258690.372094] R13: 0000000000000000 R14: ffffa05793122900 R15: ffffa0578f7cb028
[10258690.372094] FS:  0000000000000000(0000) GS:ffffa05797b40000(0000) knlGS:0000000000000000
[10258690.372094] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[10258690.372094] CR2: 00007f1a6dc00868 CR3: 000000001000e000 CR4: 00000000000006e0
[10258690.372094] Call Trace:
[10258690.372094]  <IRQ>
[10258690.372094]  skb_to_sgvec+0x11/0x40
[10258690.372094]  start_xmit+0x38c/0x520 [virtio_net]
[10258690.372094]  dev_hard_start_xmit+0x9b/0x200
[10258690.372094]  sch_direct_xmit+0xff/0x260
[10258690.372094]  __qdisc_run+0x15e/0x4e0
[10258690.372094]  net_tx_action+0x137/0x210
[10258690.372094]  __do_softirq+0xd6/0x2a9
[10258690.372094]  irq_exit+0xde/0xf0
[10258690.372094]  smp_apic_timer_interrupt+0x74/0x140
[10258690.372094]  apic_timer_interrupt+0xf/0x20
[10258690.372094]  </IRQ>

In __skb_to_sgvec(), the skb->len is not equal to the sum of the skb's
linear data size and nonlinear data size, thus BUG_ON triggered.
Because the skb is cloned and a part of nonlinear data is split off.

Duplicate packet is cloned in netem_enqueue() and may be delayed
some time in qdisc. When qdisc len reached the limit and returns
NET_XMIT_DROP, the skb will be retransmit later in write queue.
the skb will be fragmented by tso_fragment(), the limit size
that depends on cwnd and mss decrease, the skb's nonlinear
data will be split off. The length of the skb cloned by netem
will not be updated. When we use virtio_net NIC and invoke skb_to_sgvec(),
the BUG_ON trigger.

To fix it, netem returns NET_XMIT_SUCCESS to upper stack
when it clones a duplicate packet.

Fixes: 35d889d1 ("sch_netem: fix skb leak in netem_enqueue()")
Signed-off-by: Sheng Lan <lansheng@huawei.com>
Reported-by: Qin Ji <jiqin.ji@huawei.com>
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-02-28 10:31:31 -08:00
arch Bug fixes. 2019-02-24 09:47:07 -08:00
block for-linus-20190215 2019-02-15 09:12:28 -08:00
certs kbuild: remove redundant target cleaning on failure 2019-01-06 09:46:51 +09:00
crypto net: crypto set sk to NULL when af_alg_release. 2019-02-18 12:01:24 -08:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-24 09:28:26 -08:00
drivers net: phy: dp83867: add soft reset delay 2019-02-27 21:25:45 -08:00
firmware kbuild: change filechk to surround the given command with { } 2019-01-06 09:46:51 +09:00
fs Two bug fixes for old issues, both marked for stable. 2019-02-21 09:43:37 -08:00
include net: dev: Use unsigned integer as an argument to left-shift 2019-02-27 09:34:39 -08:00
init revert "initramfs: cleanup incomplete rootfs" 2019-02-21 09:00:59 -08:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-24 09:28:26 -08:00
lib Merge branch 'fixes-v5.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-02-20 09:09:33 -08:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm mm, memory_hotplug: fix off-by-one in is_pageblock_removable 2019-02-21 09:01:01 -08:00
net net: netem: fix skb length BUG_ON in __skb_to_sgvec 2019-02-28 10:31:31 -08:00
samples samples: mei: use /dev/mei0 instead of /dev/mei 2019-01-30 15:24:45 +01:00
scripts kallsyms: Handle too long symbols in kallsyms.c 2019-01-28 13:02:09 +09:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-24 09:28:26 -08:00
sound sound fixes for 5.0 2019-02-20 09:42:52 -08:00
tools selftests: pmtu: add explicit tests for PMTU exceptions cleanup 2019-02-27 21:28:59 -08:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt KVM/ARM fixes for 5.0: 2019-02-13 19:39:24 +01:00
.clang-format clang-format: Update .clang-format with the latest for_each macro list 2019-01-19 19:26:06 +01:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap A few early MIPS fixes for 4.21: 2019-01-05 12:48:25 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS CREDITS/MAINTAINERS: Retire parisc-linux.org email domain 2019-02-21 20:16:10 +01:00
Kbuild kbuild: use assignment instead of define ... endef for filechk_* rules 2019-01-06 10:22:35 +09:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-24 09:28:26 -08:00
Makefile Linux 5.0-rc7 2019-02-17 18:46:40 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.