[PATCH 5.7 348/393] fs/minix: dont allow getting deleted inodes

[Greg Kroah-Hartman]

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

commit facb03dddec04e4aac1bb2139accdceb04deb1f3 upstream.

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.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+a9ac3de1b5de5fb10...@syzkaller.appspotmail.com
Reported-by: syzbot+df958cf5688a96ad3...@syzkaller.appspotmail.com
Signed-off-by: Eric Biggers <ebigg...@google.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Cc: Qiujun Huang <anenb...@gmail.com>
Cc: <sta...@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200628060846.682158-3-ebigg...@kernel.org
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/minix/inode.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -468,6 +468,13 @@ static struct inode *V1_minix_iget(struc
                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(struc
                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);