linux-kernel - [PATCH 1/1 v2] xen: set error code on failures

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Date:   Mon,  5 Dec 2016 16:23:05 +0800
From:   Pan Bian <bianpan2016@....com>
To:     Juergen Gross <jgross@...e.com>,
        David Vrabel <david.vrabel@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org
Cc:     linux-kernel@...r.kernel.org, Pan Bian <bianpan2016@....com>
Subject: [PATCH 1/1 v2] xen: set error code on failures

Variable rc is reset in the loop, and its value will be non-negative
during the second and after repeat of the loop. If it fails to allocate
memory then, it may return a non-negative integer, which indicates no
error. This patch fixes the bug, assigning "-ENOMEM" to rc when
kzalloc() or alloc_page() returns NULL, and removing the initialization
of rc outside of the loop.

v1 is reviewed by: Juergen Gross <jgross@...e.com>

Signed-off-by: Pan Bian <bianpan2016@....com>
---
 drivers/xen/gntalloc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index 7a47c4c..1bf55a3 100644
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -127,18 +127,21 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
 	struct gntalloc_gref *gref, *next;
 
 	readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE);
-	rc = -ENOMEM;
 	for (i = 0; i < op->count; i++) {
 		gref = kzalloc(sizeof(*gref), GFP_KERNEL);
-		if (!gref)
+		if (!gref) {
+			rc = -ENOMEM;
 			goto undo;
+		}
 		list_add_tail(&gref->next_gref, &queue_gref);
 		list_add_tail(&gref->next_file, &queue_file);
 		gref->users = 1;
 		gref->file_index = op->index + i * PAGE_SIZE;
 		gref->page = alloc_page(GFP_KERNEL|__GFP_ZERO);
-		if (!gref->page)
+		if (!gref->page) {
+			rc = -ENOMEM;
 			goto undo;
+		}
 
 		/* Grant foreign access to the page. */
 		rc = gnttab_grant_foreign_access(op->domid,
-- 
1.9.1