mISDN: Fix a use after free in hfcmulti_tx()

[ Upstream commit 61ab751451f5ebd0b98e02276a44e23a10110402 ]

Don't dereference *sp after calling dev_kfree_skb(*sp).

Fixes: af69fb3a8ffa ("Add mISDN HFC multiport driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/8be65f5a-c2dd-4ba0-8a10-bfe5980b8cfb@stanley.mountain
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/isdn/hardware/mISDN/hfcmulti.c b/drivers/isdn/hardware/mISDN/hfcmulti.c
index 2e5cb9dde3ec501391f860db4f6dc8b46cd26141..44383cec1f47ad1995090ba2cfeabbed3e57f00b 100644 (file)
--- a/drivers/isdn/hardware/mISDN/hfcmulti.c
+++ b/drivers/isdn/hardware/mISDN/hfcmulti.c
@@ -1900,7 +1900,7 @@ hfcmulti_dtmf(struct hfc_multi *hc)
 static void
 hfcmulti_tx(struct hfc_multi *hc, int ch)
 {
-       int i, ii, temp, len = 0;
+       int i, ii, temp, tmp_len, len = 0;
        int Zspace, z1, z2; /* must be int for calculation */
        int Fspace, f1, f2;
        u_char *d;
@@ -2121,14 +2121,15 @@ next_frame:
                HFC_wait_nodebug(hc);
        }
 
+       tmp_len = (*sp)->len;
        dev_kfree_skb(*sp);
        /* check for next frame */
        if (bch && get_next_bframe(bch)) {
-               len = (*sp)->len;
+               len = tmp_len;
                goto next_frame;
        }
        if (dch && get_next_dframe(dch)) {
-               len = (*sp)->len;
+               len = tmp_len;
                goto next_frame;
        }