s390/ptrace: Preserve previous registers for short regset write
authorMartin Schwidefsky <schwidefsky@de.ibm.com>
Tue, 24 Jan 2017 07:05:52 +0000 (08:05 +0100)
committerMartin Schwidefsky <schwidefsky@de.ibm.com>
Tue, 24 Jan 2017 07:33:40 +0000 (08:33 +0100)
commit9dce990d2cf57b5ed4e71a9cdbd7eae4335111ff
treedfc3c82b1c6ddec3df7c0ebfcef53928d2ed2f4c
parenta4685d2f58e2230d4e27fb2ee581d7ea35e5d046
s390/ptrace: Preserve previous registers for short regset write

Ensure that if userspace supplies insufficient data to
PTRACE_SETREGSET to fill all the registers, the thread's old
registers are preserved.

convert_vx_to_fp() is adapted to handle only a specified number of
registers rather than unconditionally handling all of them: other
callers of this function are adapted appropriately.

Based on an initial patch by Dave Martin.

Cc: stable@vger.kernel.org
Reported-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
arch/s390/kernel/ptrace.c