[LTP] [PATCH v2 2/2] pty04: Add SLCAN ldisc and check for CVE-2020-11494
Richard Palethorpe
rpalethorpe@suse.com
Thu Apr 9 08:07:45 CEST 2020
Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
testcases/kernel/pty/pty04.c | 150 ++++++++++++++++++++++++++++-------
1 file changed, 120 insertions(+), 30 deletions(-)
diff --git a/testcases/kernel/pty/pty04.c b/testcases/kernel/pty/pty04.c
index d730d6834..20812edb9 100644
--- a/testcases/kernel/pty/pty04.c
+++ b/testcases/kernel/pty/pty04.c
@@ -7,6 +7,9 @@
* data is in flight to try to cause a race between the netdev being deleted
* and the discipline receive function writing to the netdev.
*
+ * For SLCAN we check stack data is not leaked in the frame padding
+ * (CVE-2020-11494).
+ *
* Test flow:
* 1. Create PTY with ldisc X which creates netdev Y
* 2. Open raw packet socket and bind to netdev Y
@@ -23,6 +26,11 @@
* until we are in the netdev code which can have a bigger buffer. Of course
* the MTU still decides exactly where the packet delimiter goes, this just
* concerns choosing the best packet size to cause a race.
+ *
+ * Note on line discipline encapsulation formats:
+ * - For SLIP frames we just write the data followed by a delimiter char
+ * - SLCAN we write some ASCII described in drivers/net/can/slcan.c which is
+ * converted to the actual frame by the kernel
*/
#define _GNU_SOURCE
@@ -36,6 +44,14 @@
#include <linux/if_ether.h>
#include <linux/tty.h>
+#ifdef HAVE_LINUX_CAN_H
+# include <linux/can.h>
+#else
+# define CAN_MTU 16
+# define CAN_MAX_DLEN 8
+#endif
+
+#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
@@ -48,19 +64,23 @@
#include "tst_safe_stdio.h"
+#define str(s) #s
+#define SLCAN_FRAME "t00185f5f5f5f5f5f5f5f\r"
+
struct ldisc_info {
int n;
char *name;
- int max_mtu;
+ int mtu;
};
static struct ldisc_info ldiscs[] = {
{N_SLIP, "N_SLIP", 8192},
+ {N_SLCAN, "N_SLCAN", CAN_MTU},
};
static volatile int ptmx, pts, sk, mtu, no_check;
-static int set_ldisc(int tty, struct ldisc_info *ldisc)
+static int set_ldisc(int tty, const struct ldisc_info *ldisc)
{
TEST(ioctl(tty, TIOCSETD, &ldisc->n));
@@ -79,7 +99,7 @@ static int set_ldisc(int tty, struct ldisc_info *ldisc)
return 1;
}
-static int open_pty(struct ldisc_info *ldisc)
+static int open_pty(const struct ldisc_info *ldisc)
{
char pts_path[PATH_MAX];
@@ -99,7 +119,8 @@ static int open_pty(struct ldisc_info *ldisc)
return set_ldisc(pts, ldisc);
}
-static ssize_t try_write(int fd, char *data, ssize_t size, ssize_t *written)
+static ssize_t try_write(int fd, const char *data,
+ ssize_t size, ssize_t *written)
{
ssize_t ret = write(fd, data, size);
@@ -109,22 +130,40 @@ static ssize_t try_write(int fd, char *data, ssize_t size, ssize_t *written)
return !written || (*written += ret) >= size;
}
-static void write_pty(void)
+static void write_pty(const struct ldisc_info *ldisc)
{
- char *data = tst_alloc(mtu);
+ char *data;
ssize_t written, ret;
+ size_t len = 0;
+
+ switch (ldisc->n) {
+ case N_SLIP:
+ len = mtu; break;
+ case N_SLCAN:
+ len = sizeof(SLCAN_FRAME) - 1; break;
+ }
+
+ data = tst_alloc(len);
+
+ switch (ldisc->n) {
+ case N_SLIP:
+ memset(data, '_', len - 1);
+ data[len - 1] = 0300;
+ break;
+ case N_SLCAN:
+ memcpy(data, SLCAN_FRAME, len);
+ break;
+ }
- memset(data, '_', mtu - 1);
- data[mtu - 1] = 0300;
written = 0;
- ret = TST_RETRY_FUNC(try_write(ptmx, data, mtu, &written), TST_RETVAL_NOTNULL);
+ ret = TST_RETRY_FUNC(try_write(ptmx, data, len, &written), TST_RETVAL_NOTNULL);
if (ret < 0)
tst_brk(TBROK | TERRNO, "Failed 1st write to PTY");
tst_res(TPASS, "Wrote PTY 1");
written = 0;
- ret = TST_RETRY_FUNC(try_write(ptmx, data, mtu, &written), TST_RETVAL_NOTNULL);
+ ret = TST_RETRY_FUNC(try_write(ptmx, data, len, &written), TST_RETVAL_NOTNULL);
if (ret < 0)
tst_brk(TBROK | TERRNO, "Failed 2nd write to PTY");
@@ -133,7 +172,7 @@ static void write_pty(void)
tst_res(TPASS, "Wrote PTY 2");
- while (try_write(ptmx, data, mtu, NULL) >= 0)
+ while (try_write(ptmx, data, len, NULL) >= 0)
;
tst_res(TPASS, "Writing to PTY interrupted by hangup");
@@ -141,7 +180,7 @@ static void write_pty(void)
tst_free_all();
}
-static void open_netdev(struct ldisc_info *ldisc)
+static void open_netdev(const struct ldisc_info *ldisc)
{
struct ifreq ifreq = { 0 };
struct sockaddr_ll lla = { 0 };
@@ -151,12 +190,12 @@ static void open_netdev(struct ldisc_info *ldisc)
sk = SAFE_SOCKET(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
- ifreq.ifr_mtu = ldisc->max_mtu;
+ ifreq.ifr_mtu = ldisc->mtu;
if (ioctl(sk, SIOCSIFMTU, &ifreq))
tst_res(TWARN | TERRNO, "Failed to set netdev MTU to maximum");
SAFE_IOCTL(sk, SIOCGIFMTU, &ifreq);
mtu = ifreq.ifr_mtu;
- tst_res(TINFO, "Netdev MTU is %d (we set %d)", mtu, ldisc->max_mtu);
+ tst_res(TINFO, "Netdev MTU is %d (we set %d)", mtu, ldisc->mtu);
SAFE_IOCTL(sk, SIOCGIFFLAGS, &ifreq);
ifreq.ifr_flags |= IFF_UP | IFF_RUNNING;
@@ -176,13 +215,45 @@ static void open_netdev(struct ldisc_info *ldisc)
tst_res(TINFO, "Bound netdev %d to socket %d", ifreq.ifr_ifindex, sk);
}
-static void check_data(const char *data, ssize_t len)
+static void check_data(const struct ldisc_info *ldisc,
+ const char *data, ssize_t len)
{
ssize_t i = 0, j;
+#ifdef HAVE_LINUX_CAN_H
+ struct can_frame frm;
+#endif
if (no_check)
return;
+#ifdef HAVE_LINUX_CAN_H
+ if (ldisc->n == N_SLCAN) {
+ memcpy(&frm, data, len);
+
+ if (frm.can_id != 1) {
+ tst_res(TFAIL, "can_id = %d != 1",
+ frm.can_id);
+ no_check = 1;
+ }
+
+ if (frm.can_dlc != CAN_MAX_DLEN) {
+ tst_res(TFAIL, "can_dlc = %d != " str(CAN_MAX_DLEN),
+ frm.can_dlc);
+ no_check = 1;
+ }
+
+ i = offsetof(struct can_frame, __pad);
+ if (frm.__pad != frm.__res0 || frm.__res0 != frm.__res1) {
+ tst_res_hexd(TFAIL, data + i,
+ offsetof(struct can_frame, data) - i,
+ "Padding bytes may contain stack data");
+ no_check = 1;
+ }
+
+ i = offsetof(struct can_frame, data);
+ }
+#endif
+
do {
if (i >= len)
return;
@@ -195,31 +266,45 @@ static void check_data(const char *data, ssize_t len)
j--;
tst_res_hexd(TFAIL, data + i, j - i,
- "Corrupt data (max 64 bytes shown): data[%ld..%ld] = ",
- i, j);
- tst_res(TINFO, "Will continue test without data checking");
+ "Corrupt data (max 64 of %ld bytes shown): data[%ld..%ld] = ",
+ len, i, j);
no_check = 1;
+
+ if (no_check)
+ tst_res(TINFO, "Will continue test without data checking");
}
-static void read_netdev(void)
+static void read_netdev(const struct ldisc_info *ldisc)
{
- int rlen, plen = mtu - 1;
- char *data = tst_alloc(plen);
+ int rlen, plen = 0;
+ char *data;
+
+ switch (ldisc->n) {
+ case N_SLIP:
+ plen = mtu - 1;
+ break;
+
+#ifdef HAVE_LINUX_CAN_H
+ case N_SLCAN:
+ plen = CAN_MTU;
+ break;
+#endif
+ }
+ data = tst_alloc(plen);
tst_res(TINFO, "Reading from socket %d", sk);
SAFE_READ(1, sk, data, plen);
- check_data(data, plen);
-
+ check_data(ldisc, data, plen);
tst_res(TPASS, "Read netdev 1");
- SAFE_READ(1, sk, data, plen);
- check_data(data, plen);
+ SAFE_READ(1, sk, data, plen);
+ check_data(ldisc, data, plen);
tst_res(TPASS, "Read netdev 2");
TST_CHECKPOINT_WAKE(0);
while((rlen = read(sk, data, plen)) > 0)
- check_data(data, rlen);
+ check_data(ldisc, data, rlen);
tst_res(TPASS, "Reading data from netdev interrupted by hangup");
@@ -236,12 +321,12 @@ static void do_test(unsigned int n)
open_netdev(ldisc);
if (!SAFE_FORK()) {
- read_netdev();
+ read_netdev(ldisc);
return;
}
if (!SAFE_FORK()) {
- write_pty();
+ write_pty(ldisc);
return;
}
@@ -268,11 +353,16 @@ static void cleanup(void)
static struct tst_test test = {
.test = do_test,
.cleanup = cleanup,
- .tcnt = 1,
+ .tcnt = 2,
.forks_child = 1,
.needs_checkpoints = 1,
.needs_root = 1,
- .min_kver = "4.10"
+ .min_kver = "4.10",
+ .tags = (const struct tst_tag[]){
+ {"linux-git", "b9258a2cece4ec1f020715fe3554bc2e360f6264"},
+ {"CVE", "CVE-2020-11494"},
+ {}
+ }
};
#else
--
2.24.0
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