[PATCH] NFSv4: fix getacl ERANGE for some ACL buffer sizes

[Weston Andros Adamson <dros@netapp.com>]

Besides storing the ACL buffer, the getacl decoder uses the inline
pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
must allocate enough page space for all of the data to be decoded.

This bug results in getxattr() returning ERANGE when the attr buffer
length is close enough to the nearest PAGE_SIZE multiple that adding
the extra bytes leaves too little room for the ACL buffer.

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
---
 fs/nfs/nfs4proc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 5ab33c0..006cba1 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4453,7 +4453,12 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
 		.rpc_argp = &args,
 		.rpc_resp = &res,
 	};
-	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
+	/*
+	 * extra space needed for attr bitmap and length in getacl decoder.
+	 * 1 word for bitmap len, 3 words for bitmaps and 1 word for attr len.
+	 */
+	unsigned int preamble_len = 20;
+	unsigned int npages = DIV_ROUND_UP(preamble_len + buflen, PAGE_SIZE);
 	int ret = -ENOMEM, i;
 
 	/* As long as we're doing a round trip to the server anyway,
-- 
1.8.3.1 (Apple Git-46)