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    Subject[PATCH 5.4 081/177] ovl: relax WARN_ON() on rename to self
    Date
    From: Amir Goldstein <amir73il@gmail.com>

    commit 6889ee5a53b8d969aa542047f5ac8acdc0e79a91 upstream.

    In ovl_rename(), if new upper is hardlinked to old upper underneath
    overlayfs before upper dirs are locked, user will get an ESTALE error
    and a WARN_ON will be printed.

    Changes to underlying layers while overlayfs is mounted may result in
    unexpected behavior, but it shouldn't crash the kernel and it shouldn't
    trigger WARN_ON() either, so relax this WARN_ON().

    Reported-by: syzbot+bb1836a212e69f8e201a@syzkaller.appspotmail.com
    Fixes: 804032fabb3b ("ovl: don't check rename to self")
    Cc: <stable@vger.kernel.org> # v4.9+
    Signed-off-by: Amir Goldstein <amir73il@gmail.com>
    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/overlayfs/dir.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/fs/overlayfs/dir.c
    +++ b/fs/overlayfs/dir.c
    @@ -1170,7 +1170,7 @@ static int ovl_rename(struct inode *oldd
    if (newdentry == trap)
    goto out_dput;

    - if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
    + if (olddentry->d_inode == newdentry->d_inode)
    goto out_dput;

    err = 0;

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