[PATCH 3.16 163/212] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Ben Hutchings]

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

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

From: Weston Andros Adamson <dros@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/nfs/nfs4proc.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4444,7 +4444,7 @@ 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,
@@ -4458,13 +4458,9 @@ 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;
 
-	/* 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;