linux-kernel - Re: [PATCH 1/5] ima: Set file->f_mode instead of file->f_flags in ima_calc_file

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Message-Id: <1587556981.5738.7.camel@linux.ibm.com>
Date:   Wed, 22 Apr 2020 08:03:01 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, krzysztof.struczynski@...wei.com,
        silviu.vlasceanu@...wei.com, stable@...r.kernel.org,
        Goldwyn Rodrigues <rgoldwyn@...e.com>
Subject: Re: [PATCH 1/5] ima: Set file->f_mode instead of file->f_flags in
 ima_calc_file_hash()

[CC'ing Goldwyn Rodrigues]

Hi Roberto,

On Wed, 2020-03-25 at 17:11 +0100, Roberto Sassu wrote:
> Commit a408e4a86b36 ("ima: open a new file instance if no read
> permissions") tries to create a new file descriptor to calculate a file
> digest if the file has not been opened with O_RDONLY flag. However, if a
> new file descriptor cannot be obtained, it sets the FMODE_READ flag to
> file->f_flags instead of file->f_mode.
> 
> This patch fixes this issue by replacing f_flags with f_mode as it was
> before that commit.
> 
> Cc: stable@...r.kernel.org # 4.20.x
> Fixes: a408e4a86b36 ("ima: open a new file instance if no read permissions")
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
>  security/integrity/ima/ima_crypto.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
> index 423c84f95a14..8ab17aa867dd 100644
> --- a/security/integrity/ima/ima_crypto.c
> +++ b/security/integrity/ima/ima_crypto.c
> @@ -436,7 +436,7 @@ int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
>  			 */

Thanks, Roberto.  The comment above here and the rest of the code
refers to flags.  Both should be updated as well to reflect using
f_mode.

>  			pr_info_ratelimited("Unable to reopen file for reading.\n");
>  			f = file;
> -			f->f_flags |= FMODE_READ;
> +			f->f_mode |= FMODE_READ;
>  			modified_flags = true;

The variable should be changed to "modified_mode".

thanks,

Mimi

>  		} else {
>  			new_file_instance = true;
> @@ -456,7 +456,7 @@ int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
>  	if (new_file_instance)
>  		fput(f);
>  	else if (modified_flags)
> -		f->f_flags &= ~FMODE_READ;
> +		f->f_mode &= ~FMODE_READ;
>  	return rc;
>  }
>