tty: n_gsm: improper skb_pull() use was leaking framed data

gsm_dlci_data_output_framed() was doing:
memcpy(dp, skb_pull(dlci->skb, len), len);

The problem is skb_pull() returns the post-increment data ptr
so the first chunk of dlci->skb->data is leaked.

Signed-off-by: Russ Gorby <russ.gorby@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 7290394e3131..19b4ae052af8 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -875,7 +875,8 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
                 *dp++ = last << 7 | first << 6 | 1;     /* EA */
                 len--;
         }
-        memcpy(dp, skb_pull(dlci->skb, len), len);
+        memcpy(dp, dlci->skb->data, len);
+        skb_pull(dlci->skb, len);
         __gsm_data_queue(dlci, msg);
         if (last)
                 dlci->skb = NULL;