[PATCH AUTOSEL 4.9 03/12] s390/dasd: fix using offset into zero size array error

Sasha Levin
2019-03-11T20:02:14Z

From: Stefan Haberland <sth@linux.ibm.com>

[ Upstream commit 4a8ef6999bce998fa5813023a9a6b56eea329dba ]

Dan Carpenter reported the following:

The patch 52898025cf7d: "[S390] dasd: security and PSF update patch
for EMC CKD ioctl" from Mar 8, 2010, leads to the following static
checker warning:

drivers/s390/block/dasd_eckd.c:4486 dasd_symm_io()
error: using offset into zero size array 'psf_data[]'

drivers/s390/block/dasd_eckd.c
4458 /* Copy parms from caller */
4459 rc = -EFAULT;
4460 if (copy_from_user(&usrparm, argp, sizeof(usrparm)))
^^^^^^^
The user can specify any "usrparm.psf_data_len". They choose zero by
mistake.

4461 goto out;
4462 if (is_compat_task()) {
4463 /* Make sure pointers are sane even on 31 bit. */
4464 rc = -EINVAL;
4465 if ((usrparm.psf_data >> 32) != 0)
4466 goto out;
4467 if ((usrparm.rssd_result >> 32) != 0)
4468 goto out;
4469 usrparm.psf_data &= 0x7fffffffULL;
4470 usrparm.rssd_result &= 0x7fffffffULL;
4471 }
4472 /* alloc I/O data area */
4473 psf_data = kzalloc(usrparm.psf_data_len, GFP_KERNEL
| GFP_DMA);
4474 rssd_result = kzalloc(usrparm.rssd_result_len, GFP_KERNEL
| GFP_DMA);
4475 if (!psf_data || !rssd_result) {

kzalloc() returns a ZERO_SIZE_PTR (0x16).

4476 rc = -ENOMEM;
4477 goto out_free;
4478 }
4479
4480 /* get syscall header from user space */
4481 rc = -EFAULT;
4482 if (copy_from_user(psf_data,
4483 (void __user *)(unsigned long)
usrparm.psf_data,
4484 usrparm.psf_data_len))

That all works great.

4485 goto out_free;
4486 psf0 = psf_data[0];
4487 psf1 = psf_data[1];

But now we're assuming that "->psf_data_len" was at least 2 bytes.

Fix this by checking the user specified length psf_data_len.

Fixes: 52898025cf7d ("[S390] dasd: security and PSF update patch for EMC CKD ioctl")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/s390/block/dasd_eckd.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index be17de9807b6..11c6335b1951 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -4508,6 +4508,14 @@ static int dasd_symm_io(struct dasd_device *device, void __user *argp)
usrparm.psf_data &= 0x7fffffffULL;
usrparm.rssd_result &= 0x7fffffffULL;
}
+ /* at least 2 bytes are accessed and should be allocated */
+ if (usrparm.psf_data_len < 2) {
+ DBF_DEV_EVENT(DBF_WARNING, device,
+ "Symmetrix ioctl invalid data length %d",
+ usrparm.psf_data_len);
+ rc = -EINVAL;
+ goto out;
+ }
/* alloc I/O data area */
psf_data = kzalloc(usrparm.psf_data_len, GFP_KERNEL | GFP_DMA);
rssd_result = kzalloc(usrparm.rssd_result_len, GFP_KERNEL | GFP_DMA);
--
2.19.1