Hello,
I believe i have stumbled upon a documentation inconsistency
concerning securelevels and usage of /dev/io
From init(8) manpage
1 Secure mode - the system immutable and system append-only flags may
not be turned off; disks for mounted file systems, /dev/mem,
/dev/kmem and /dev/io (if your platform has it) may not be opened
for writing; kernel modules (see kld(4)) may not be loaded or
unloaded.
Note the "may not be opened for writing". It is correct for /dev/mem
and /dev/kmem but incorrect for /dev/io as the following experiment
shows:
3:40pm ~ # sysctl kern.securelevel
kern.securelevel: 1
[EMAIL PROTECTED]
3:40pm ~ # head /dev/io
head: /dev/io: Operation not permitted
[EMAIL PROTECTED]
3:40pm ~ #
Now the source code in /usr/src/sys/i386/i386/io.c just checks if
securelevel is greater that 0 when opening the device and return
accordingly.
However from io(4)
Note that even read-only access will grant the full I/O privileges.
Which means that changing the code to check if the device is opened
O_RDONLY and then allowing access would be a mistake cancelling the
idea of blocking access to the device through usage of the
securelevel.
I am correct about the above ?
Does the documentation need a correction in that place?
Thanks,
alex
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