linux-kernel - [ 109/143] isdnloop: several buffer overflows

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Date:	Mon, 12 May 2014 02:33:49 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	"David S. Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu>
Subject: [ 109/143] isdnloop: several buffer overflows

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit 7563487cbf865284dcd35e9ef5a95380da046737 ]

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@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/isdn/isdnloop/isdnloop.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/isdn/isdnloop/isdnloop.c b/drivers/isdn/isdnloop/isdnloop.c
index 92d895f..bf4168b 100644
--- a/drivers/isdn/isdnloop/isdnloop.c
+++ b/drivers/isdn/isdnloop/isdnloop.c
@@ -517,9 +517,9 @@ 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);
 }
@@ -902,6 +902,8 @@ 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:
@@ -1126,7 +1128,7 @@ isdnloop_command(isdn_ctrl * c, isdnloop_card * card)
 {
 	ulong a;
 	int i;
-	char cbuf[60];
+	char cbuf[80];
 	isdn_ctrl cmd;
 	isdnloop_cdef cdef;

@@ -1191,7 +1193,6 @@ 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;
@@ -1203,10 +1204,10 @@ 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;
-- 
1.7.12.2.21.g234cd45.dirty

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