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    Subject[PATCH 4.14 106/109] ima: relax requiring a file signature for new files with zero length
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Mimi Zohar <zohar@linux.vnet.ibm.com>


    [ Upstream commit b7e27bc1d42e8e0cc58b602b529c25cd0071b336 ]

    Custom policies can require file signatures based on LSM labels. These
    files are normally created and only afterwards labeled, requiring them
    to be signed.

    Instead of requiring file signatures based on LSM labels, entire
    filesystems could require file signatures. In this case, we need the
    ability of writing new files without requiring file signatures.

    The definition of a "new" file was originally defined as any file with
    a length of zero. Subsequent patches redefined a "new" file to be based
    on the FILE_CREATE open flag. By combining the open flag with a file
    size of zero, this patch relaxes the file signature requirement.

    Fixes: 1ac202e978e1 ima: accept previously set IMA_NEW_FILE
    Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    security/integrity/ima/ima_appraise.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/security/integrity/ima/ima_appraise.c
    +++ b/security/integrity/ima/ima_appraise.c
    @@ -223,7 +223,8 @@ int ima_appraise_measurement(enum ima_ho
    if (opened & FILE_CREATED)
    iint->flags |= IMA_NEW_FILE;
    if ((iint->flags & IMA_NEW_FILE) &&
    - !(iint->flags & IMA_DIGSIG_REQUIRED))
    + (!(iint->flags & IMA_DIGSIG_REQUIRED) ||
    + (inode->i_size == 0)))
    status = INTEGRITY_PASS;
    goto out;
    }

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