zkey: correctly detect abbreviated commands
zkey: correctly detect abbreviated commands

Abbreviated commands are not recognized and zkey issues an invalid
command error.

In is_command(), the abbreviated command string is copied into the
command_str variable.  Because this variable is not initialized and,
thus, might contain arbitrary data, a NUL-terminated is not guaranteed.
The following string comparison is very likely to fail.  Correct this
problem by comparing up to the length of the command string only.

Signed-off-by: Hendrik Brueckner <ea0a2d16c17dd61debc108adbc0ac849646dd099@linux.vnet.ibm.com>
Signed-off-by: Michael Holzheu <db4757c56f54651f568cc7cda79cd93c781b1605@linux.vnet.ibm.com>

ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools