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    Subject[PATCH 3.14 17/84] CIFS: fix type confusion in copy offload ioctl
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jann Horn <jann@thejh.net>

    commit 4c17a6d56bb0cad3066a714e94f7185a24b40f49 upstream.

    This might lead to local privilege escalation (code execution as
    kernel) for systems where the following conditions are met:

    - CONFIG_CIFS_SMB2 and CONFIG_CIFS_POSIX are enabled
    - a cifs filesystem is mounted where:
    - the mount option "vers" was used and set to a value >=2.0
    - the attacker has write access to at least one file on the filesystem

    To attack this, an attacker would have to guess the target_tcon
    pointer (but guessing wrong doesn't cause a crash, it just returns an
    error code) and win a narrow race.

    Signed-off-by: Jann Horn <jann@thejh.net>
    Signed-off-by: Steve French <smfrench@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/cifs/ioctl.c | 6 ++++++
    1 file changed, 6 insertions(+)

    --- a/fs/cifs/ioctl.c
    +++ b/fs/cifs/ioctl.c
    @@ -67,6 +67,12 @@ static long cifs_ioctl_clone(unsigned in
    goto out_drop_write;
    }

    + if (src_file.file->f_op->unlocked_ioctl != cifs_ioctl) {
    + rc = -EBADF;
    + cifs_dbg(VFS, "src file seems to be from a different filesystem type\n");
    + goto out_fput;
    + }
    +
    if ((!src_file.file->private_data) || (!dst_file->private_data)) {
    rc = -EBADF;
    cifs_dbg(VFS, "missing cifsFileInfo on copy range src file\n");



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