nilfs2: add more check routines in mount process

nilfs2: Add more safeguard routines and protections in mount process,
which also makes nilfs2 report consistency error messages when
checkpoint number is invalid.

Signed-off-by: Zhu Yanhai <zhu.yanhai@gmail.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

2 files changed, 14 insertions, 4 deletions

diff --git a/fs/nilfs2/cpfile.c b/fs/nilfs2/cpfile.c
index aec942cf79e3..1c6cfb59128d 100644
--- a/fs/nilfs2/cpfile.c
+++ b/fs/nilfs2/cpfile.c
@@ -815,8 +815,10 @@ int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
         void *kaddr;
         int ret;
 
-        if (cno == 0)
-                return -ENOENT; /* checkpoint number 0 is invalid */
+        /* CP number is invalid if it's zero or larger than the
+        largest exist one.*/
+        if (cno == 0 || cno >= nilfs_mdt_cno(cpfile))
+                return -ENOENT;
         down_read(&NILFS_MDT(cpfile)->mi_sem);
 
         ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
@@ -824,7 +826,10 @@ int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
                 goto out;
         kaddr = kmap_atomic(bh->b_page, KM_USER0);
         cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
-        ret = nilfs_checkpoint_snapshot(cp);
+        if (nilfs_checkpoint_invalid(cp))
+                ret = -ENOENT;
+        else
+                ret = nilfs_checkpoint_snapshot(cp);
         kunmap_atomic(kaddr, KM_USER0);
         brelse(bh);
 
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 019752f7d2da..50284add7880 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -792,10 +792,15 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
 
         if (sb->s_flags & MS_RDONLY) {
                 if (nilfs_test_opt(sbi, SNAPSHOT)) {
+                        down_read(&nilfs->ns_segctor_sem);
                         err = nilfs_cpfile_is_snapshot(nilfs->ns_cpfile,
                                                        sbi->s_snapshot_cno);
-                        if (err < 0)
+                        up_read(&nilfs->ns_segctor_sem);
+                        if (err < 0) {
+                                if (err == -ENOENT)
+                                        err = -EINVAL;
                                 goto failed_sbi;
+                        }
                         if (!err) {
                                 printk(KERN_ERR
                                        "NILFS: The specified checkpoint is "