[PATCH 4.9 086/175] NFSv4.2: condition READDIRs mask for security label based on LSM state

[Greg Kroah-Hartman]

From: Olga Kornievskaia <kolga@xxxxxxxxxx>

[ Upstream commit 05ad917561fca39a03338cb21fe9622f998b0f9c ]

Currently, the client will always ask for security_labels if the server
returns that it supports that feature regardless of any LSM modules
(such as Selinux) enforcing security policy. This adds performance
penalty to the READDIR operation.

Client adjusts superblock's support of the security_label based on
the server's support but also current client's configuration of the
LSM modules. Thus, prior to using the default bitmask in READDIR,
this patch checks the server's capabilities and then instructs
READDIR to remove FATTR4_WORD2_SECURITY_LABEL from the bitmask.

v5: fixing silly mistakes of the rushed v4
v4: simplifying logic
v3: changing label's initialization per Ondrej's comment
v2: dropping selinux hook and using the sb cap.

Suggested-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
Suggested-by: Scott Mayhew <smayhew@xxxxxxxxxx>
Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
Fixes: 2b0143b5c986 ("VFS: normal filesystems (and lustre): d_inode() annotations")
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/nfs/nfs4proc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 4e2f18c26535d..2abdb2070c879 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4334,12 +4334,12 @@ static int _nfs4_proc_readdir(struct dentry *dentry, struct rpc_cred *cred,
 		u64 cookie, struct page **pages, unsigned int count, int plus)
 {
 	struct inode		*dir = d_inode(dentry);
+	struct nfs_server	*server = NFS_SERVER(dir);
 	struct nfs4_readdir_arg args = {
 		.fh = NFS_FH(dir),
 		.pages = pages,
 		.pgbase = 0,
 		.count = count,
-		.bitmask = NFS_SERVER(d_inode(dentry))->attr_bitmask,
 		.plus = plus,
 	};
 	struct nfs4_readdir_res res;
@@ -4354,9 +4354,15 @@ static int _nfs4_proc_readdir(struct dentry *dentry, struct rpc_cred *cred,
 	dprintk("%s: dentry = %pd2, cookie = %Lu\n", __func__,
 			dentry,
 			(unsigned long long)cookie);
+	if (!(server->caps & NFS_CAP_SECURITY_LABEL))
+		args.bitmask = server->attr_bitmask_nl;
+	else
+		args.bitmask = server->attr_bitmask;
+
 	nfs4_setup_readdir(cookie, NFS_I(dir)->cookieverf, dentry, &args);
 	res.pgbase = args.pgbase;
-	status = nfs4_call_sync(NFS_SERVER(dir)->client, NFS_SERVER(dir), &msg, &args.seq_args, &res.seq_res, 0);
+	status = nfs4_call_sync(server->client, server, &msg, &args.seq_args,
+			&res.seq_res, 0);
 	if (status >= 0) {
 		memcpy(NFS_I(dir)->cookieverf, res.verifier.data, NFS4_VERIFIER_SIZE);
 		status += args.pgbase;
-- 
2.27.0