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d0ba3f1f58
[ Upstream commit 2459dcb96bcba94c08d6861f8a050185ff301672 ]
IFLA_IFNAME is nul-term string which means that IFLA_IFNAME buffer can be
larger than length of string which contains.
Function __rtnl_newlink() generates new own ifname if either IFLA_IFNAME
was not specified at all or userspace passed empty nul-term string.
It is expected that if userspace does not specify ifname for new ppp netdev
then kernel generates one in format "ppp<id>" where id matches to the ppp
unit id which can be later obtained by PPPIOCGUNIT ioctl.
And it works in this way if IFLA_IFNAME is not specified at all. But it
does not work when IFLA_IFNAME is specified with empty string.
So fix this logic also for empty IFLA_IFNAME in ppp_nl_newlink() function
and correctly generates ifname based on ppp unit identifier if userspace
did not provided preferred ifname.
Without this patch when IFLA_IFNAME was specified with empty string then
kernel created a new ppp interface in format "ppp<id>" but id did not
match ppp unit id returned by PPPIOCGUNIT ioctl. In this case id was some
number generated by __rtnl_newlink() function.
Signed-off-by: Pali Rohár <pali@kernel.org>
Fixes: bb8082f69138 ("ppp: build ifname using unit identifier for rtnl based devices")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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.