[patch 2/2] misc: mic/scif: fix wrap around tests

[Dan Carpenter <dan.carpenter@oracle.com>]

Signed integer overflow is undefined.  Also I added a check for
"(offset < 0)" in scif_unregister() because that makes it match the
other conditions and because I didn't want to subtract a negative.

Fixes: ba612aa8b487 ('misc: mic: SCIF memory registration and unregistration')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---

Imagine you are on 64 bit and len is larger than INT_MAX << 12, it means
that we truncate it because scif_get_window_offset() takes an integer
argument.  I don't know if this is an issue.  Maybe I should use
INT_MAX instead of LONG_MAX?  I am working on a static checker warning
for these types of issues:
drivers/misc/mic/scif/scif_rma.c:1631 scif_register() warn: truncating user data 'len >> 12' '0-4503599627370495'
drivers/misc/mic/scif/scif_rma.c:1643 scif_register() warn: truncating user data 'len >> 12' '0-4503599627370495'

The other static warnings here are:

drivers/misc/mic/scif/scif_rma.c:745 scif_unregister_window() warn: inconsistent returns 'mutex:&ep->rma_info.rma_lock'.
  Locked on:   line 745
  Unlocked on: line 687
drivers/misc/mic/scif/scif_rma.c:1463 scif_unpin_pages() warn: passing __func__ while the format string already contains the name of the function 'scif_unpin_pages'

diff --git a/drivers/misc/mic/scif/scif_rma.c b/drivers/misc/mic/scif/scif_rma.c
index bc2dccb..fea7d2c 100644
--- a/drivers/misc/mic/scif/scif_rma.c
+++ b/drivers/misc/mic/scif/scif_rma.c
@@ -1510,7 +1510,7 @@ off_t scif_register_pinned_pages(scif_epd_t epd,
 	if ((map_flags & SCIF_MAP_FIXED) &&
 	    ((ALIGN(offset, PAGE_SIZE) != offset) ||
 	    (offset < 0) ||
-	    (offset + (off_t)len < offset)))
+	    (len > LONG_MAX - offset)))
 		return -EINVAL;
 
 	might_sleep();
@@ -1613,7 +1613,7 @@ off_t scif_register(scif_epd_t epd, void *addr, size_t len, off_t offset,
 	if ((map_flags & SCIF_MAP_FIXED) &&
 	    ((ALIGN(offset, PAGE_SIZE) != offset) ||
 	    (offset < 0) ||
-	    (offset + (off_t)len < offset)))
+	    (len < LONG_MAX - offset)))
 		return -EINVAL;
 
 	/* Unsupported protection requested */
@@ -1731,7 +1731,8 @@ scif_unregister(scif_epd_t epd, off_t offset, size_t len)
 
 	/* Offset is not page aligned or offset+len wraps around */
 	if ((ALIGN(offset, PAGE_SIZE) != offset) ||
-	    (offset + (off_t)len < offset))
+	    (offset < 0) ||
+	    (len > LONG_MAX - offset))
 		return -EINVAL;
 
 	err = scif_verify_epd(ep);