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    Subject[PATCH 4.14 067/183] stm class: Prevent division by zero
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Alexander Shishkin <alexander.shishkin@linux.intel.com>

    commit bf7cbaae0831252b416f375ca9b1027ecd4642dd upstream.

    Using STP_POLICY_ID_SET ioctl command with dummy_stm device, or any STM
    device that supplies zero mmio channel size, will trigger a division by
    zero bug in the kernel.

    Prevent this by disallowing channel widths other than 1 for such devices.

    Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices")
    CC: stable@vger.kernel.org # v4.4+
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/hwtracing/stm/core.c | 8 +++++---
    1 file changed, 5 insertions(+), 3 deletions(-)

    --- a/drivers/hwtracing/stm/core.c
    +++ b/drivers/hwtracing/stm/core.c
    @@ -561,7 +561,7 @@ static int stm_char_policy_set_ioctl(str
    {
    struct stm_device *stm = stmf->stm;
    struct stp_policy_id *id;
    - int ret = -EINVAL;
    + int ret = -EINVAL, wlimit = 1;
    u32 size;

    if (stmf->output.nr_chans)
    @@ -589,8 +589,10 @@ static int stm_char_policy_set_ioctl(str
    if (id->__reserved_0 || id->__reserved_1)
    goto err_free;

    - if (id->width < 1 ||
    - id->width > PAGE_SIZE / stm->data->sw_mmiosz)
    + if (stm->data->sw_mmiosz)
    + wlimit = PAGE_SIZE / stm->data->sw_mmiosz;
    +
    + if (id->width < 1 || id->width > wlimit)
    goto err_free;

    ret = stm_file_assign(stmf, id->id, id->width);

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