Make nfs_file_cred more robust.

As not all files have an associated open_context (e.g. device special
files), it is safest to test for the existence of the open context
before de-referencing it.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 10 insertions, 4 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index c910413eaeca..83e700a2b0c0 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1659,8 +1659,10 @@ nfs4_proc_setattr(struct dentry *dentry, struct nfs_fattr *fattr,
                 struct nfs_open_context *ctx;
 
                 ctx = nfs_file_open_context(sattr->ia_file);
-                cred = ctx->cred;
-                state = ctx->state;
+                if (ctx) {
+                        cred = ctx->cred;
+                        state = ctx->state;
+                }
         }
 
         status = nfs4_do_setattr(inode, cred, fattr, sattr, state);
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index ac8d0233b05c..4eaa8347a0d9 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -367,8 +367,12 @@ static inline struct nfs_open_context *nfs_file_open_context(struct file *filp)
 
 static inline struct rpc_cred *nfs_file_cred(struct file *file)
 {
-        if (file != NULL)
-                return nfs_file_open_context(file)->cred;
+        if (file != NULL) {
+                struct nfs_open_context *ctx =
+                        nfs_file_open_context(file);
+                if (ctx)
+                        return ctx->cred;
+        }
         return NULL;
 }