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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Roberto Bergantinos Corpas <rbergant@redhat.com>,
        Pavel Shilovsky <pshilov@microsoft.com>,
        Steve French <stfrench@microsoft.com>
Subject: [PATCH 4.14 59/69] CIFS: cifs_read_allocate_pages: dont iterate through whole page array on ENOMEM
Date:   Fri,  7 Jun 2019 17:39:40 +0200
Message-Id: <20190607153855.358636577@linuxfoundation.org>
In-Reply-To: <20190607153848.271562617@linuxfoundation.org>
References: <20190607153848.271562617@linuxfoundation.org>
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From: Roberto Bergantinos Corpas <rbergant@redhat.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@redhat.com>
Acked-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/cifs/file.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2984,7 +2984,9 @@ 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;
 		}