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* [v2 1/1] i2c: dev: prevent ZERO_SIZE_PTR deref in i2cdev_ioctl_rdwr()
@ 2018-04-19 12:29 Alexander Popov
  2018-04-19 13:49 ` Uwe Kleine-König
  2018-04-27 12:06 ` Wolfram Sang
  0 siblings, 2 replies; 7+ messages in thread
From: Alexander Popov @ 2018-04-19 12:29 UTC (permalink / raw)
  To: Wolfram Sang, Uwe Kleine-König, linux-i2c, linux-kernel,
	sil2review, Dmitry Vyukov, syzkaller, Alexander Popov

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>
---
 drivers/i2c/i2c-dev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 036a03f..5790bc8 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -280,6 +280,7 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
 		 */
 		if (msgs[i].flags & I2C_M_RECV_LEN) {
 			if (!(msgs[i].flags & I2C_M_RD) ||
+			    !msgs[i].len ||
 			    msgs[i].buf[0] < 1 ||
 			    msgs[i].len < msgs[i].buf[0] +
 					     I2C_SMBUS_BLOCK_MAX) {
-- 
2.7.4

^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2018-04-30  7:13 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-04-19 12:29 [v2 1/1] i2c: dev: prevent ZERO_SIZE_PTR deref in i2cdev_ioctl_rdwr() Alexander Popov
2018-04-19 13:49 ` Uwe Kleine-König
2018-04-19 17:01   ` Alexander Popov
2018-04-20  5:58     ` Uwe Kleine-König
2018-04-23 20:18   ` Alexander Popov
2018-04-27 12:06 ` Wolfram Sang
2018-04-30  7:13   ` Uwe Kleine-König

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