Re: [PATCH 06/20] ima: Manual replacement of the deprecated strlcpy() with return values

Mimi Zohar
2021-03-02T13:30:30Z

On Mon, 2021-02-22 at 16:12 +0100, Romain Perier wrote:
> The strlcpy() reads the entire source buffer first, it is dangerous if
> the source buffer lenght is unbounded or possibility non NULL-terminated.

As other's have pointed out, "lenght" -> length.

> It can lead to linear read overflows, crashes, etc...
>
> As recommended in the deprecated interfaces [1], it should be replaced
> by strscpy.
>
> This commit replaces all calls to strlcpy that handle the return values
> by the corresponding strscpy calls with new handling of the return
> values (as it is quite different between the two functions).
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
>
> Signed-off-by: Romain Perier <romain.perier@gmail.com>
> ---
> security/integrity/ima/ima_policy.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 9b45d064a87d..1a905b8b064f 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -790,8 +790,14 @@ static int __init ima_init_arch_policy(void)
> for (rules = arch_rules, i = 0; *rules != NULL; rules++) {
> char rule[255];
> int result;
> + ssize_t len;
>
> - result = strlcpy(rule, *rules, sizeof(rule));
> + len = strscpy(rule, *rules, sizeof(rule));
> + if (len == -E2BIG) {
> + pr_warn("Internal copy of architecture policy rule '%s' "
> + "failed. Skipping.\n", *rules);

"arch_rules" is an array of hard coded strings. The generic reason
for replacing strlcpy with strscpy doesn't seem applicable; however,
the additonal warning is appropriate.

(User-visible strings are not bound to the 80 column length. Breaking
up the line like this is fine, but unnecessary.)

Acked-by: Mimi Zohar <zohar@linux.ibm.com>

thanks,

Mimi

> + continue;
> + }
>
> INIT_LIST_HEAD(&arch_policy_entry[i].list);
> result = ima_parse_rule(rule, &arch_policy_entry[i]);
>