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    Subject[PATCH 4.4 112/149] fs/minix: dont allow getting deleted inodes
    Date
    From: Eric Biggers <ebiggers@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+a9ac3de1b5de5fb10efc@syzkaller.appspotmail.com
    Reported-by: syzbot+df958cf5688a96ad3287@syzkaller.appspotmail.com
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Cc: Alexander Viro <viro@zeniv.linux.org.uk>
    Cc: Qiujun Huang <anenbupt@gmail.com>
    Cc: <stable@vger.kernel.org>
    Link: http://lkml.kernel.org/r/20200628060846.682158-3-ebiggers@kernel.org
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

    --- a/fs/minix/inode.c
    +++ b/fs/minix/inode.c
    @@ -472,6 +472,13 @@ 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);
    @@ -505,6 +512,13 @@ 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);

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