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Pali Rohár bffead8d36 ppp: Fix generating ppp unit id when ifname is not specified 
commit 3125f26c51 upstream.

When registering new ppp interface via PPPIOCNEWUNIT ioctl then kernel has
to choose interface name as this ioctl API does not support specifying it.

Kernel in this case register new interface with name "ppp<id>" where <id>
is the ppp unit id, which can be obtained via PPPIOCGUNIT ioctl. This
applies also in the case when registering new ppp interface via rtnl
without supplying IFLA_IFNAME.

PPPIOCNEWUNIT ioctl allows to specify own ppp unit id which will kernel
assign to ppp interface, in case this ppp id is not already used by other
ppp interface.

In case user does not specify ppp unit id then kernel choose the first free
ppp unit id. This applies also for case when creating ppp interface via
rtnl method as it does not provide a way for specifying own ppp unit id.

If some network interface (does not have to be ppp) has name "ppp<id>"
with this first free ppp id then PPPIOCNEWUNIT ioctl or rtnl call fails.

And registering new ppp interface is not possible anymore, until interface
which holds conflicting name is renamed. Or when using rtnl method with
custom interface name in IFLA_IFNAME.

As list of allocated / used ppp unit ids is not possible to retrieve from
kernel to userspace, userspace has no idea what happens nor which interface
is doing this conflict.

So change the algorithm how ppp unit id is generated. And choose the first
number which is not neither used as ppp unit id nor in some network
interface with pattern "ppp<id>".

This issue can be simply reproduced by following pppd call when there is no
ppp interface registered and also no interface with name pattern "ppp<id>":

    pppd ifname ppp1 +ipv6 noip noauth nolock local nodetach pty "pppd +ipv6 noip noauth nolock local nodetach notty"

Or by creating the one ppp interface (which gets assigned ppp unit id 0),
renaming it to "ppp1" and then trying to create a new ppp interface (which
will always fails as next free ppp unit id is 1, but network interface with
name "ppp1" exists).

This patch fixes above described issue by generating new and new ppp unit
id until some non-conflicting id with network interfaces is generated.

Signed-off-by: Pali Rohár <pali@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-08-15 14:00:26 +02:00
arch arm64: dts: renesas: beacon: Fix USB ref clock references 2021-08-15 14:00:25 +02:00
block blk-iolatency: error out if blk_get_queue() failed in iolatency_set_limit() 2021-08-12 13:22:08 +02:00
certs certs: add 'x509_revocation_list' to gitignore 2021-07-20 16:05:35 +02:00
crypto crypto: sm2 - fix a memory leak in sm2 2021-07-14 16:56:06 +02:00
Documentation Documentation: Fix intiramfs script name 2021-07-28 14:35:47 +02:00
drivers ppp: Fix generating ppp unit id when ifname is not specified 2021-08-15 14:00:26 +02:00
fs vboxsf: Make vboxsf_dir_create() return the handle for the created file 2021-08-15 14:00:26 +02:00
include mm: make zone_to_nid() and zone_set_nid() available for DISCONTIGMEM 2021-08-15 14:00:25 +02:00
init sched/core: Initialize the idle task with preemption disabled 2021-07-14 16:55:50 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-26 12:06:54 +02:00
kernel bpf: Add lockdown check for probe_write_user helper 2021-08-15 14:00:25 +02:00
lib net: add kcov handle to skb extensions 2021-07-28 14:35:33 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm memblock: make for_each_mem_range() traverse MEMBLOCK_HOTPLUG regions 2021-07-28 14:35:46 +02:00
net net/xfrm/compat: Copy xfrm_spdattr_type_t atributes 2021-08-12 13:22:16 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 16:56:23 +02:00
scripts scripts/tracing: fix the bug that can't parse raw_trace_func 2021-08-12 13:22:12 +02:00
security bpf: Add lockdown check for probe_write_user helper 2021-08-15 14:00:25 +02:00
sound ALSA: hda: Add quirk for ASUS Flow x13 2021-08-15 14:00:26 +02:00
tools Revert "selftests/resctrl: Use resctrl/info for feature detection" 2021-08-15 14:00:25 +02:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: Do not leak memory for duplicate debugfs directories 2021-08-12 13:22:17 +02:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS f2fs: move ioctl interface definitions to separated file 2021-05-19 10:13:00 +02:00
Makefile Linux 5.10.58 2021-08-12 13:22:21 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.