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    Subject[PATCH 4.9 28/66] s390/ptrace: Preserve previous registers for short regset write
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Martin Schwidefsky <schwidefsky@de.ibm.com>

    commit 9dce990d2cf57b5ed4e71a9cdbd7eae4335111ff upstream.

    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.

    Reported-by: Dave Martin <Dave.Martin@arm.com>
    Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/s390/kernel/ptrace.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    --- a/arch/s390/kernel/ptrace.c
    +++ b/arch/s390/kernel/ptrace.c
    @@ -963,6 +963,11 @@ static int s390_fpregs_set(struct task_s
    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
    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++)

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