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>

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 7447ba5..12020b5 100644 (file)
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -963,6 +963,11 @@ static int s390_fpregs_set(struct task_struct *target,
        if (target == current)
                save_fpu_regs();
 
+       if (MACHINE_HAS_VX)
+               convert_vx_to_fp(fprs, target->thread.fpu.vxrs);
+       else
+               memcpy(&fprs, target->thread.fpu.fprs, sizeof(fprs));
+
        /* If setting FPC, must validate it first. */
        if (count > 0 && pos < offsetof(s390_fp_regs, fprs)) {
                u32 ufpc[2] = { target->thread.fpu.fpc, 0 };
@@ -1067,6 +1072,9 @@ static int s390_vxrs_low_set(struct task_struct *target,
        if (target == current)
                save_fpu_regs();
 
+       for (i = 0; i < __NUM_VXRS_LOW; i++)
+               vxrs[i] = *((__u64 *)(target->thread.fpu.vxrs + i) + 1);
+
        rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vxrs, 0, -1);
        if (rc == 0)
                for (i = 0; i < __NUM_VXRS_LOW; i++)