s390/dasd: fix using offset into zero size array error

Stefan Haberland · Martin Schwidefsky · commit 4a8ef6999bce · 2019-01-28T15:43:17.000+01:00
Dan Carpenter reported the following: The patch 5289802: "[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: 5289802 ("[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>
diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
@@ -4469,6 +4469,14 @@ 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);
