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David Woodhouse f93d65939a atm: Preserve value of skb->truesize when accounting to vcc 
[ Upstream commit 9bbe60a67b ]

ATM accounts for in-flight TX packets in sk_wmem_alloc of the VCC on
which they are to be sent. But it doesn't take ownership of those
packets from the sock (if any) which originally owned them. They should
remain owned by their actual sender until they've left the box.

There's a hack in pskb_expand_head() to avoid adjusting skb->truesize
for certain skbs, precisely to avoid messing up sk_wmem_alloc
accounting. Ideally that hack would cover the ATM use case too, but it
doesn't — skbs which aren't owned by any sock, for example PPP control
frames, still get their truesize adjusted when the low-level ATM driver
adds headroom.

This has always been an issue, it seems. The truesize of a packet
increases, and sk_wmem_alloc on the VCC goes negative. But this wasn't
for normal traffic, only for control frames. So I think we just got away
with it, and we probably needed to send 2GiB of LCP echo frames before
the misaccounting would ever have caused a problem and caused
atm_may_send() to start refusing packets.

Commit 14afee4b60 ("net: convert sock.sk_wmem_alloc from atomic_t to
refcount_t") did exactly what it was intended to do, and turned this
mostly-theoretical problem into a real one, causing PPPoATM to fail
immediately as sk_wmem_alloc underflows and atm_may_send() *immediately*
starts refusing to allow new packets.

The least intrusive solution to this problem is to stash the value of
skb->truesize that was accounted to the VCC, in a new member of the
ATM_SKB(skb) structure. Then in atm_pop_raw() subtract precisely that
value instead of the then-current value of skb->truesize.

Fixes: 158f323b98 ("net: adjust skb->truesize in pskb_expand_head()")
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Tested-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2018-07-22 14:28:43 +02:00
Documentation kbuild: delete INSTALL_FW_PATH from kbuild documentation 2018-07-17 11:39:30 +02:00
arch x86/paravirt: Make native_save_fl() extern inline 2018-07-22 14:28:42 +02:00
block block: cope with WRITE ZEROES failing in blkdev_issue_zeroout() 2018-07-11 16:29:19 +02:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto crypto: x86/salsa20 - remove x86 salsa20 implementations 2018-07-17 11:39:31 +02:00
drivers alx: take rtnl before calling __alx_open from resume 2018-07-22 14:28:43 +02:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs ocfs2: ip_alloc_sem should be taken in ocfs2_get_block() 2018-07-22 14:28:42 +02:00
include atm: Preserve value of skb->truesize when accounting to vcc 2018-07-22 14:28:43 +02:00
init init: fix false positives in W+X checking 2018-06-21 04:02:57 +09:00
ipc ipc/shm: fix shmat() nil address after round-down when remapping 2018-05-30 07:51:49 +02:00
kernel PM / hibernate: Fix oops at snapshot_write() 2018-07-17 11:39:32 +02:00
lib lib/vsprintf: Remove atomic-unsafe support for %pCr 2018-07-03 11:24:48 +02:00
mm mm: do not bug_on on incorrect length in __mm_populate() 2018-07-17 11:39:29 +02:00
net atm: Preserve value of skb->truesize when accounting to vcc 2018-07-22 14:28:43 +02:00
samples samples/bpf: Partially fixes the bpf.o build 2018-04-26 11:02:12 +02:00
scripts Kbuild: fix # escaping in .cmd files for future Make 2018-07-11 16:29:21 +02:00
security selinux: KASAN: slab-out-of-bounds in xattr_getsecurity 2018-06-05 11:41:56 +02:00
sound ALSA: hda - Handle pm failure during hotplug 2018-07-17 11:39:29 +02:00
tools tools build: fix # escaping in .cmd files for future Make 2018-07-17 11:39:30 +02:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: vgic: fix possible spectre-v1 in vgic_mmio_read_apr() 2018-06-21 04:02:49 +09:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING
…
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS dt-bindings: Document mti,mips-cpc binding 2018-03-15 10:54:35 +01:00
Makefile Linux 4.14.56 2018-07-17 11:39:34 +02:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.