isdnloop: several buffer overflows

There are three buffer overflows addressed in this patch.

1) In isdnloop_fake_err() we add an 'E' to a 60 character string and
then copy it into a 60 character buffer.  I have made the destination
buffer 64 characters and I'm changed the sprintf() to a snprintf().

2) In isdnloop_parse_cmd(), p points to a 6 characters into a 60
character buffer so we have 54 characters.  The ->eazlist[] is 11
characters long.  I have modified the code to return if the source
buffer is too long.

3) In isdnloop_command() the cbuf[] array was 60 characters long but the
max length of the string then can be up to 79 characters.  I made the
cbuf array 80 characters long and changed the sprintf() to snprintf().
I also removed the temporary "dial" buffer and changed it to use "p"
directly.

Unfortunately, we pass the "cbuf" string from isdnloop_command() to
isdnloop_writecmd() which truncates anything over 60 characters to make
it fit in card->omsg[].  (It can accept values up to 255 characters so
long as there is a '\n' character every 60 characters).  For now I have
just fixed the memory corruption bug and left the other problems in this
driver alone.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 8 deletions

diff --git a/drivers/isdn/isdnloop/isdnloop.c b/drivers/isdn/isdnloop/isdnloop.c
index e1f8748ff25d..5a4da94aefb0 100644
--- a/drivers/isdn/isdnloop/isdnloop.c
+++ b/drivers/isdn/isdnloop/isdnloop.c
@@ -518,9 +518,9 @@ static isdnloop_stat isdnloop_cmd_table[] =
 static void
 isdnloop_fake_err(isdnloop_card *card)
 {
-        char buf[60];
+        char buf[64];
 
-        sprintf(buf, "E%s", card->omsg);
+        snprintf(buf, sizeof(buf), "E%s", card->omsg);
         isdnloop_fake(card, buf, -1);
         isdnloop_fake(card, "NAK", -1);
 }
@@ -903,6 +903,8 @@ isdnloop_parse_cmd(isdnloop_card *card)
         case 7:
                 /* 0x;EAZ */
                 p += 3;
+                if (strlen(p) >= sizeof(card->eazlist[0]))
+                        break;
                 strcpy(card->eazlist[ch - 1], p);
                 break;
         case 8:
@@ -1133,7 +1135,7 @@ isdnloop_command(isdn_ctrl *c, isdnloop_card *card)
 {
         ulong a;
         int i;
-        char cbuf[60];
+        char cbuf[80];
         isdn_ctrl cmd;
         isdnloop_cdef cdef;
 
@@ -1198,7 +1200,6 @@ isdnloop_command(isdn_ctrl *c, isdnloop_card *card)
                         break;
                 if ((c->arg & 255) < ISDNLOOP_BCH) {
                         char *p;
-                        char dial[50];
                         char dcode[4];
 
                         a = c->arg;
@@ -1210,10 +1211,10 @@ isdnloop_command(isdn_ctrl *c, isdnloop_card *card)
                         } else
                                 /* Normal Dial */
                                 strcpy(dcode, "CAL");
-                        strcpy(dial, p);
-                        sprintf(cbuf, "%02d;D%s_R%s,%02d,%02d,%s\n", (int) (a + 1),
-                                dcode, dial, c->parm.setup.si1,
-                                c->parm.setup.si2, c->parm.setup.eazmsn);
+                        snprintf(cbuf, sizeof(cbuf),
+                                 "%02d;D%s_R%s,%02d,%02d,%s\n", (int) (a + 1),
+                                 dcode, p, c->parm.setup.si1,
+                                 c->parm.setup.si2, c->parm.setup.eazmsn);
                         i = isdnloop_writecmd(cbuf, strlen(cbuf), 0, card);
                 }
                 break;