From a81072a9c0ae734b7889929b0bc070fe3f353f0e Mon Sep 17 00:00:00 2001
From: Souptick Joarder <jrdr.linux@gmail.com>
Date: Sun, 20 Sep 2020 08:21:35 +0530
Subject: [PATCH] misc: mic: scif: Fix error handling path
Git-commit: a81072a9c0ae734b7889929b0bc070fe3f353f0e
Patch-mainline: v5.10-rc1
References: git-fixes

Inside __scif_pin_pages(), when map_flags != SCIF_MAP_KERNEL it
will call pin_user_pages_fast() to map nr_pages. However,
pin_user_pages_fast() might fail with a return value -ERRNO.

The return value is stored in pinned_pages->nr_pages. which in
turn is passed to unpin_user_pages(), which expects
pinned_pages->nr_pages >=0, else disaster.

Fix this by assigning pinned_pages->nr_pages to 0 if
pin_user_pages_fast() returns -ERRNO.

Fixes: ba612aa8b487 ("misc: mic: SCIF memory registration and unregistration")
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Link: https://lore.kernel.org/r/1600570295-29546-1-git-send-email-jrdr.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/misc/mic/scif/scif_rma.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/misc/mic/scif/scif_rma.c
+++ b/drivers/misc/mic/scif/scif_rma.c
@@ -1403,6 +1403,8 @@ retry:
 				NULL);
 		up_write(&mm->mmap_sem);
 		if (nr_pages != pinned_pages->nr_pages) {
+			if (pinned_pages->nr_pages < 0)
+				pinned_pages->nr_pages = 0;
 			if (try_upgrade) {
 				if (ulimit)
 					__scif_dec_pinned_vm_lock(mm,
@@ -1423,7 +1425,6 @@ retry:
 
 	if (pinned_pages->nr_pages < nr_pages) {
 		err = -EFAULT;
-		pinned_pages->nr_pages = nr_pages;
 		goto dec_pinned;
 	}
 
@@ -1436,7 +1437,6 @@ dec_pinned:
 		__scif_dec_pinned_vm_lock(mm, nr_pages, 0);
 	/* Something went wrong! Rollback */
 error_unmap:
-	pinned_pages->nr_pages = nr_pages;
 	scif_destroy_pinned_pages(pinned_pages);
 	*pages = NULL;
 	dev_dbg(scif_info.mdev.this_device,