linux-kernel - [PATCH] NFS: fix access bit translation in _nfs4_proc

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Date:   Fri, 10 Nov 2017 16:03:56 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Trond Myklebust <trond.myklebust@...marydata.com>,
        Anna Schumaker <anna.schumaker@...app.com>
Cc:     linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de, patchwork-lst@...gutronix.de
Subject: [PATCH] NFS: fix access bit translation in _nfs4_proc_access()

Since bd8b2441742b (NFS: Store the raw NFS access mask in the inode's
access cache) the mask already contains the NFS access bits, so it is
wrong to try to map them from the MAY_* bits to the NFS_MAY_* bits
in _nfs4_proc_access(). This leads to bogus access permissions being
returned from the server.

Fix this by using the mask directly, but be careful to not ask for
to broad permissions from the calling nfs_do_access().

CC: stable@...r.kernel.org #4.13+
Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
Tested-by: Björn Lässig <b.laessig@...gutronix.de>
---
 fs/nfs/dir.c      |  8 ++++++--
 fs/nfs/nfs4proc.c | 19 +------------------
 2 files changed, 7 insertions(+), 20 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 5ceaeb1f6fb6..dd3a06353bdc 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2426,8 +2426,12 @@ static int nfs_do_access(struct inode *inode, struct rpc_cred *cred, int mask)
 		goto out;
 
 	/* Be clever: ask server to check for all possible rights */
-	cache.mask = NFS_MAY_LOOKUP | NFS_MAY_EXECUTE
-		     | NFS_MAY_WRITE | NFS_MAY_READ;
+	cache.mask = NFS_MAY_READ;
+	if (S_ISDIR(inode->i_mode))
+		cache.mask |= NFS_DIR_MAY_WRITE | NFS_MAY_LOOKUP;
+	else
+		cache.mask |= NFS_FILE_MAY_WRITE | NFS_MAY_EXECUTE;
+
 	cache.cred = cred;
 	status = NFS_PROTO(inode)->access(inode, &cache);
 	if (status != 0) {
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 6c61e2b99635..cb7b5aafaef6 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3889,6 +3889,7 @@ static int _nfs4_proc_access(struct inode *inode, struct nfs_access_entry *entry
 	struct nfs4_accessargs args = {
 		.fh = NFS_FH(inode),
 		.bitmask = server->cache_consistency_bitmask,
+		.access = entry->mask,
 	};
 	struct nfs4_accessres res = {
 		.server = server,
@@ -3899,26 +3900,8 @@ static int _nfs4_proc_access(struct inode *inode, struct nfs_access_entry *entry
 		.rpc_resp = &res,
 		.rpc_cred = entry->cred,
 	};
-	int mode = entry->mask;
 	int status = 0;
 
-	/*
-	 * Determine which access bits we want to ask for...
-	 */
-	if (mode & MAY_READ)
-		args.access |= NFS4_ACCESS_READ;
-	if (S_ISDIR(inode->i_mode)) {
-		if (mode & MAY_WRITE)
-			args.access |= NFS4_ACCESS_MODIFY | NFS4_ACCESS_EXTEND | NFS4_ACCESS_DELETE;
-		if (mode & MAY_EXEC)
-			args.access |= NFS4_ACCESS_LOOKUP;
-	} else {
-		if (mode & MAY_WRITE)
-			args.access |= NFS4_ACCESS_MODIFY | NFS4_ACCESS_EXTEND;
-		if (mode & MAY_EXEC)
-			args.access |= NFS4_ACCESS_EXECUTE;
-	}
-
 	res.fattr = nfs_alloc_fattr();
 	if (res.fattr == NULL)
 		return -ENOMEM;
-- 
2.11.0