[PATCH 5.15 132/230] tty: n_gsm: fix sometimes uninitialized warning in gsm_dlci_modem_output()

Greg Kroah-Hartman
2022-07-11T09:55:23Z

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