[PATCH 5.15.y] nfsd: gate nfs2 setacl by argp->mask

[Sasha Levin <sashal@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

[ Upstream commit a3a7e20ed66d3f04d37883c398da8a113b430769 ]

The NFSACL v2 SETACL path shares the decoder convention used by its
v3 sibling: nfsaclsvc_decode_setaclargs() fills in argp->acl_access
only when NFS_ACL is set in the request mask and argp->acl_default
only when NFS_DFACL is set, leaving the other pointer NULL because
the argument buffer is zeroed up to pc_argzero before decode.

nfsacld_proc_setacl() then hands both pointers to set_posix_acl()
unconditionally. set_posix_acl(idmap, dentry, type, NULL) is the VFS
"remove this ACL type" operation, so an omitted arm is
indistinguishable from an explicit request to delete that ACL. A
SETACL carrying only NFS_ACL silently strips the directory's default
ACL; mask=0 strips both.

This is the same defect just fixed in nfsd3_proc_setacl(); apply the
same remedy. Gate each set_posix_acl() call on its mask bit and
initialize error to 0 so that a request with neither bit set leaves
the on-disk ACLs untouched and returns success. The out_drop_lock
path and the unconditional posix_acl_release() in
nfsaclsvc_release_setacl() already tolerate the skipped arms.

Fixes: a257cdd0e217 ("[PATCH] NFSD: Add server support for NFSv3 ACLs.")
Cc: stable@vger.kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
[ retained the older user-namespace and inode set_posix_acl() API in place of the newer mount-idmap and dentry API. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfsd/nfs2acl.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/fs/nfsd/nfs2acl.c b/fs/nfsd/nfs2acl.c
index 44b74d83560b5..6e2ed6947033c 100644
--- a/fs/nfsd/nfs2acl.c
+++ b/fs/nfsd/nfs2acl.c
@@ -115,14 +115,19 @@ static __be32 nfsacld_proc_setacl(struct svc_rqst *rqstp)
 
 	inode_lock(inode);
 
-	error = set_posix_acl(&init_user_ns, inode, ACL_TYPE_ACCESS,
-			      argp->acl_access);
-	if (error)
-		goto out_drop_lock;
-	error = set_posix_acl(&init_user_ns, inode, ACL_TYPE_DEFAULT,
-			      argp->acl_default);
-	if (error)
-		goto out_drop_lock;
+	error = 0;
+	if (argp->mask & NFS_ACL) {
+		error = set_posix_acl(&init_user_ns, inode, ACL_TYPE_ACCESS,
+				      argp->acl_access);
+		if (error)
+			goto out_drop_lock;
+	}
+	if (argp->mask & NFS_DFACL) {
+		error = set_posix_acl(&init_user_ns, inode, ACL_TYPE_DEFAULT,
+				      argp->acl_default);
+		if (error)
+			goto out_drop_lock;
+	}
 
 	inode_unlock(inode);
 
-- 
2.53.0