d59577b6ff
While a privileged program can open a raw socket, attach some restrictive filter and drop its privileges (or send the socket to an unprivileged program through some Unix socket), the filter can still be removed or modified by the unprivileged program. This commit adds a socket option to lock the filter (SO_LOCK_FILTER) preventing any modification of a socket filter program. This is similar to OpenBSD BIOCLOCK ioctl on bpf sockets, except even root is not allowed change/drop the filter. The state of the lock can be read with getsockopt(). No error is triggered if the state is not changed. -EPERM is returned when a user tries to remove the lock or to change/remove the filter while the lock is active. The check is done directly in sk_attach_filter() and sk_detach_filter() and does not affect only setsockopt() syscall. Signed-off-by: Vincent Bernat <bernat@luffy.cx> Signed-off-by: David S. Miller <davem@davemloft.net> |
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