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This patch enables the "/proc/sys/net/unix/max_dgram_qlen" sysctl to be exposed to non-init user namespaces. max_dgram_qlen is used as the default "sk_max_ack_backlog" value for when a unix socket is created. Currently, when a networking namespace is initialized, its unix sysctls are exposed only if the user namespace that "owns" it is the init user namespace. If there is an non-init user namespace that "owns" a networking namespace (for example, in the case after we call clone() with both CLONE_NEWUSER and CLONE_NEWNET set), the sysctls are hidden from view and not configurable. Exposing the unix sysctl is safe because any changes made to it will be limited in scope to the networking namespace the non-init user namespace "owns" and has privileges over (changes won't affect any other net namespace). There is also no possibility of a non-privileged user namespace messing up the net namespace sysctls it shares with its parent user namespace. When a new user namespace is created without unsharing the network namespace (eg calling clone() with CLONE_NEWUSER), the new user namespace shares its parent's network namespace. Write access is protected by the mode set in the sysctl's ctl_table (and enforced by procfs). Here in the case of "max_dgram_qlen", 0644 is set; only the user owner has write access. v1 -> v2: * Add more detail to commit message, specify the "/proc/sys/net/unix/max_dgram_qlen" sysctl in commit message. Signed-off-by: Joanne Koong <joannekoong@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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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.