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    Subject[PATCH 5.15 132/230] tty: n_gsm: fix sometimes uninitialized warning in gsm_dlci_modem_output()
    Date
    From: Daniel Starke <daniel.starke@siemens.com>

    [ Upstream commit 19317433057dc1f2ca9a975e4e6b547282c2a5ef ]

    'size' may be used uninitialized in gsm_dlci_modem_output() if called with
    an adaption that is neither 1 nor 2. The function is currently only called
    by gsm_modem_upd_via_data() and only for adaption 2.
    Properly handle every invalid case by returning -EINVAL to silence the
    compiler warning and avoid future regressions.

    Fixes: c19ffe00fed6 ("tty: n_gsm: fix invalid use of MSC in advanced option")
    Cc: stable@vger.kernel.org
    Reported-by: kernel test robot <lkp@intel.com>
    Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
    Link: https://lore.kernel.org/r/20220425104726.7986-1-daniel.starke@siemens.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/tty/n_gsm.c | 15 +++++++++------
    1 file changed, 9 insertions(+), 6 deletions(-)

    diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
    index c8ca00fad8e4..fd4a86111a6e 100644
    --- a/drivers/tty/n_gsm.c
    +++ b/drivers/tty/n_gsm.c
    @@ -945,18 +945,21 @@ static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci,
    {
    u8 *dp = NULL;
    struct gsm_msg *msg;
    - int size;
    + int size = 0;

    /* for modem bits without break data */
    - if (dlci->adaption == 1) {
    - size = 0;
    - } else if (dlci->adaption == 2) {
    - size = 1;
    + switch (dlci->adaption) {
    + case 1: /* Unstructured */
    + break;
    + case 2: /* Unstructured with modem bits. */
    + size++;
    if (brk > 0)
    size++;
    - } else {
    + break;
    + default:
    pr_err("%s: unsupported adaption %d\n", __func__,
    dlci->adaption);
    + return -EINVAL;
    }

    msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
    --
    2.35.1


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