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[4.14,1/1] i2c: dev: prevent ZERO_SIZE_PTR deref in i2cdev_ioctl_rdwr()

Message ID 20221003084346.4652-2-harshit.m.mogalapalli@oracle.com
State New
Headers show
Series Fix NULL dereference in i2cdev_ioctl_rdwr() | expand

Commit Message

Harshit Mogalapalli Oct. 3, 2022, 8:43 a.m. UTC
From: Alexander Popov <alex.popov@linux.com>

commit 23a27722b5292ef0b27403c87a109feea8296a5c upstream.

i2cdev_ioctl_rdwr() allocates i2c_msg.buf using memdup_user(), which
returns ZERO_SIZE_PTR if i2c_msg.len is zero.

Currently i2cdev_ioctl_rdwr() always dereferences the buf pointer in case
of I2C_M_RD | I2C_M_RECV_LEN transfer. That causes a kernel oops in
case of zero len.

Let's check the len against zero before dereferencing buf pointer.

This issue was triggered by syzkaller.

Signed-off-by: Alexander Popov <alex.popov@linux.com>
Reviewed-by: Uwe Kleine-K├Ânig <u.kleine-koenig@pengutronix.de>
[wsa: use '< 1' instead of '!' for easier readability]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
[Harshit: backport to 4.14.y, use rdwr_pa[i].len instead of msgs[i].len
as the 4.14.y  code uses rdwr_pa.]
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
---
 Conflicts:
	drivers/i2c/i2c-dev.c - use rdwr_pa[i].len instead of
	msgs[i].len
Since a NULL pointer dereference happens on 4.14.y this backport patch
will fix the issue.
---
 drivers/i2c/i2c-dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index b7f9fb00f695..08aff5ebc99a 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -297,7 +297,7 @@  static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
 		 */
 		if (rdwr_pa[i].flags & I2C_M_RECV_LEN) {
 			if (!(rdwr_pa[i].flags & I2C_M_RD) ||
-			    rdwr_pa[i].buf[0] < 1 ||
+			    rdwr_pa[i].len < 1 || rdwr_pa[i].buf[0] < 1 ||
 			    rdwr_pa[i].len < rdwr_pa[i].buf[0] +
 					     I2C_SMBUS_BLOCK_MAX) {
 				i++;