sysctl: allow override of /proc/sys/net with CAP_NET_ADMIN
Extend the permission check for networking sysctl's to allow modification when current process has CAP_NET_ADMIN capability and is not root. This version uses the until now unused permissions hook to override the mode value for /proc/sys/net if accessed by a user with capabilities. Found while working with Quagga. It is impossible to turn forwarding on/off through the command interface because Quagga uses secure coding practice of dropping privledges during initialization and only raising via capabilities when necessary. Since the dameon has reset real/effective uid after initialization, all attempts to access /proc/sys/net variables will fail. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Chris Wright <chrisw@sous-sol.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrew Morgan <morgan@kernel.org> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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