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.carpen...@oracle.com>
---
I reversed a condition in the first version of this patch.

diff --git a/drivers/misc/mic/scif/scif_rma.c b/drivers/misc/mic/scif/scif_rma.c
index bc2dccb..245ea9b 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);
--
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