linux-kernel - [PATCH 3.16 34/87] CIFS: cifs_read_allocate_pages: don't iterate through whole page array on ENOMEM

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Message-ID: <lsq.1570043211.957725814@decadent.org.uk>
Date:   Wed, 02 Oct 2019 20:06:51 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Pavel Shilovsky" <pshilov@...rosoft.com>,
        "Steve French" <stfrench@...rosoft.com>,
        "Roberto Bergantinos Corpas" <rbergant@...hat.com>
Subject: [PATCH 3.16 34/87] CIFS: cifs_read_allocate_pages: don't iterate
 through whole page array on ENOMEM

3.16.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Roberto Bergantinos Corpas <rbergant@...hat.com>

commit 31fad7d41e73731f05b8053d17078638cf850fa6 upstream.

 In cifs_read_allocate_pages, in case of ENOMEM, we go through
whole rdata->pages array but we have failed the allocation before
nr_pages, therefore we may end up calling put_page with NULL
pointer, causing oops

Signed-off-by: Roberto Bergantinos Corpas <rbergant@...hat.com>
Acked-by: Pavel Shilovsky <pshilov@...rosoft.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/cifs/file.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2744,7 +2744,9 @@ cifs_read_allocate_pages(struct cifs_rea
 	}
 
 	if (rc) {
-		for (i = 0; i < nr_pages; i++) {
+		unsigned int nr_page_failed = i;
+
+		for (i = 0; i < nr_page_failed; i++) {
 			put_page(rdata->pages[i]);
 			rdata->pages[i] = NULL;
 		}