nfsd: don't fail unchecked creates of non-special files

Allow a v3 unchecked open of a non-regular file succeed as if it were a
lookup; typically a client in such a case will want to fall back on a
local open, so succeeding and giving it the filehandle is more useful
than failing with nfserr_exist, which makes it appear that nothing at
all exists by that name.

Similarly for v4, on an open-create, return the same errors we would on
an attempt to open a non-regular file, instead of returning
nfserr_exist.

This fixes a problem found doing a v4 open of a symlink with
O_RDONLY|O_CREAT, which resulted in the current client returning EEXIST.

Thanks also to Trond for analysis.

Cc: stable@kernel.org
Reported-by: Orion Poplawski <orion@cora.nwra.com>
Tested-by: Orion Poplawski <orion@cora.nwra.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

2 files changed, 5 insertions, 5 deletions

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 2ed14dfd00a2..8256efda3638 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -235,17 +235,17 @@ do_open_lookup(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_o
                  */
                 if (open->op_createmode == NFS4_CREATE_EXCLUSIVE && status == 0)
                         open->op_bmval[1] = (FATTR4_WORD1_TIME_ACCESS |
-                                                FATTR4_WORD1_TIME_MODIFY);
+                                                        FATTR4_WORD1_TIME_MODIFY);
         } else {
                 status = nfsd_lookup(rqstp, current_fh,
                                      open->op_fname.data, open->op_fname.len, resfh);
                 fh_unlock(current_fh);
-                if (status)
-                        goto out;
-                status = nfsd_check_obj_isreg(resfh);
         }
         if (status)
                 goto out;
+        status = nfsd_check_obj_isreg(resfh);
+        if (status)
+                goto out;
 
         if (is_create_with_attrs(open) && open->op_acl != NULL)
                 do_set_nfs4_acl(rqstp, resfh, open->op_acl, open->op_bmval);
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 296d671654d6..568666156ea4 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1458,7 +1458,7 @@ do_nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 switch (createmode) {
                 case NFS3_CREATE_UNCHECKED:
                         if (! S_ISREG(dchild->d_inode->i_mode))
-                                err = nfserr_exist;
+                                goto out;
                         else if (truncp) {
                                 /* in nfsv4, we need to treat this case a little
                                  * differently.  we don't want to truncate the