reiserfs: check kstrdup failure

Check out-of-memory failure of the kstrdup option. Note that the argument
"arg" may be NULL (in that case kstrup returns NULL), so out of memory
condition happened if arg was non-NULL and kstrdup returned NULL.

The patch also changes the call to replace_mount_options - if we didn't
pass any filesystem-specific options, we don't call replace_mount_options
(thus we don't erase existing reported options).

Note that to properly report options after remount, the reiserfs
filesystem should implement the show_options method. Without the
show_options method, options changed with remount replace existing
options.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/reiserfs/super.c

@@ -1393,7 +1393,7 @@ static int reiserfs_remount(struct super_block *s, int *mount_flags, char *arg)
 	unsigned long safe_mask = 0;
 	unsigned int commit_max_age = (unsigned int)-1;
 	struct reiserfs_journal *journal = SB_JOURNAL(s);
-	char *new_opts = kstrdup(arg, GFP_KERNEL);
+	char *new_opts;
 	int err;
 	char *qf_names[REISERFS_MAXQUOTAS];
 	unsigned int qfmt = 0;
@@ -1401,6 +1401,10 @@ static int reiserfs_remount(struct super_block *s, int *mount_flags, char *arg)
 	int i;
 #endif
 
+	new_opts = kstrdup(arg, GFP_KERNEL);
+	if (arg && !new_opts)
+		return -ENOMEM;
+
 	sync_filesystem(s);
 	reiserfs_write_lock(s);
 
@@ -1546,6 +1550,7 @@ static int reiserfs_remount(struct super_block *s, int *mount_flags, char *arg)
 	}
 
 out_ok_unlocked:
+	if (new_opts)
 		replace_mount_options(s, new_opts);
 	return 0;