linux-kernel - [PATCH 3.2 064/101] NFSv4: fix getacl ERANGE for some ACL buffer sizes

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Message-ID: <lsq.1496331655.516306148@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:40:55 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Anna Schumaker" <Anna.Schumaker@...app.com>,
        "J. Bruce Fields" <bfields@...hat.com>,
        "Weston Andros Adamson" <dros@...marydata.com>
Subject: [PATCH 3.2 064/101] NFSv4: fix getacl ERANGE for some ACL buffer
 sizes

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

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

From: Weston Andros Adamson <dros@...marydata.com>

commit ed92d8c137b7794c2c2aa14479298b9885967607 upstream.

We're not taking into account that the space needed for the (variable
length) attr bitmap, with the result that we'd sometimes get a spurious
ERANGE when the ACL data got close to the end of a page.

Just add in an extra page to make sure.

Signed-off-by: Weston Andros Adamson <dros@...marydata.com>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/nfs/nfs4proc.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3569,7 +3569,7 @@ out:
  */
 static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t buflen)
 {
-	struct page *pages[NFS4ACL_MAXPAGES] = {NULL, };
+	struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };
 	struct nfs_getaclargs args = {
 		.fh = NFS_FH(inode),
 		.acl_pages = pages,
@@ -3583,14 +3583,10 @@ static ssize_t __nfs4_get_acl_uncached(s
 		.rpc_argp = &args,
 		.rpc_resp = &res,
 	};
-	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
+	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE) + 1;
 	int ret = -ENOMEM, i;
 	size_t acl_len = 0;
 
-	/* As long as we're doing a round trip to the server anyway,
-	 * let's be prepared for a page of acl data. */
-	if (npages == 0)
-		npages = 1;
 	if (npages > ARRAY_SIZE(pages))
 		return -ERANGE;