[PATCH 2/6] fs/minix: don't allow getting deleted inodes

[Eric Biggers]

From: Eric Biggers <ebigg...@google.com>

If an inode has no links, we need to mark it bad rather than allowing it
to be accessed.  This avoids WARNINGs in inc_nlink() and drop_nlink()
when doing directory operations on a fuzzed filesystem.

Reported-by: syzbot+a9ac3de1b5de5fb10...@syzkaller.appspotmail.com
Reported-by: syzbot+df958cf5688a96ad3...@syzkaller.appspotmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: sta...@vger.kernel.org
Signed-off-by: Eric Biggers <ebigg...@google.com>
---
 fs/minix/inode.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/minix/inode.c b/fs/minix/inode.c
index 7cb5fd38eb14..2bca95abe8f4 100644
--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -468,6 +468,13 @@ static struct inode *V1_minix_iget(struct inode *inode)
                iget_failed(inode);
                return ERR_PTR(-EIO);
        }
+       if (raw_inode->i_nlinks == 0) {
+               printk("MINIX-fs: deleted inode referenced: %lu\n",
+                      inode->i_ino);
+               brelse(bh);
+               iget_failed(inode);
+               return ERR_PTR(-ESTALE);
+       }
        inode->i_mode = raw_inode->i_mode;
        i_uid_write(inode, raw_inode->i_uid);
        i_gid_write(inode, raw_inode->i_gid);
@@ -501,6 +508,13 @@ static struct inode *V2_minix_iget(struct inode *inode)
                iget_failed(inode);
                return ERR_PTR(-EIO);
        }
+       if (raw_inode->i_nlinks == 0) {
+               printk("MINIX-fs: deleted inode referenced: %lu\n",
+                      inode->i_ino);
+               brelse(bh);
+               iget_failed(inode);
+               return ERR_PTR(-ESTALE);
+       }
        inode->i_mode = raw_inode->i_mode;
        i_uid_write(inode, raw_inode->i_uid);
        i_gid_write(inode, raw_inode->i_gid);
-- 
2.27.0