nfsd4: permit read opens of executable-only files

A client that wants to execute a file must be able to read it.  Read
opens over nfs are therefore implicitly allowed for executable files
even when those files are not readable.

NFSv2/v3 get this right by using a passed-in NFSD_MAY_OWNER_OVERRIDE on
read requests, but NFSv4 has gotten this wrong ever since
dc730e173785e29b297aa605786c94adaffe2544 "nfsd4: fix owner-override on
open", when we realized that the file owner shouldn't override
permissions on non-reclaim NFSv4 opens.

So we can't use NFSD_MAY_OWNER_OVERRIDE to tell nfsd_permission to allow
reads of executable files.

So, do the same thing we do whenever we encounter another weird NFS
permission nit: define yet another NFSD_MAY_* flag.

The industry's future standardization on 128-bit processors will be
motivated primarily by the need for integers with enough bits for all
the NFSD_MAY_* flags.

Reported-by: Leonardo Borda <leonardoborda@gmail.com>
Cc: stable@kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 479ffb185df9..b5530984db91 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -156,6 +156,8 @@ do_open_permission(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfs
                 !(open->op_share_access & NFS4_SHARE_ACCESS_WRITE))
                 return nfserr_inval;
 
+        accmode |= NFSD_MAY_READ_IF_EXEC;
+
         if (open->op_share_access & NFS4_SHARE_ACCESS_READ)
                 accmode |= NFSD_MAY_READ;
         if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE)