linux-kernel - Re: [PATCH 03/12] ima: Free the entire rule when deleting a list of rules

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Message-ID: <1593119109.27152.393.camel@linux.ibm.com>
Date:   Thu, 25 Jun 2020 17:05:09 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Tyler Hicks <tyhicks@...ux.microsoft.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>
Cc:     James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        Prakhar Srivastava <prsriva02@...il.com>,
        linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH 03/12] ima: Free the entire rule when deleting a list of
 rules

On Mon, 2020-06-22 at 19:32 -0500, Tyler Hicks wrote:
> Use ima_free_rule() to fix memory leaks of allocated ima_rule_entry
> members, such as .fsname and .keyrings, when deleting a list of rules.
> 
> This fixes a memory leak seen when loading by a valid rule that contains
> an additional piece of allocated memory, such as an fsname, followed by
> an invalid rule that triggers a policy load failure:
> 
>  # echo -e "dont_measure fsname=securityfs\nbad syntax" > \
>     /sys/kernel/security/ima/policy
>  -bash: echo: write error: Invalid argument
>  # echo scan > /sys/kernel/debug/kmemleak
>  # cat /sys/kernel/debug/kmemleak
>  unreferenced object 0xffff9bab67ca12c0 (size 16):
>    comm "tee", pid 684, jiffies 4295212803 (age 252.344s)
>    hex dump (first 16 bytes):
>      73 65 63 75 72 69 74 79 66 73 00 6b 6b 6b 6b a5  securityfs.kkkk.
>    backtrace:
>      [<00000000adc80b1b>] kstrdup+0x2e/0x60
>      [<00000000d504cb0d>] ima_parse_add_rule+0x7d4/0x1020
>      [<00000000444825ac>] ima_write_policy+0xab/0x1d0
>      [<000000002b7f0d6c>] vfs_write+0xde/0x1d0
>      [<0000000096feedcf>] ksys_write+0x68/0xe0
>      [<0000000052b544a2>] do_syscall_64+0x56/0xa0
>      [<000000007ead1ba7>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Fixes: f1b08bbcbdaf ("ima: define a new policy condition based on the filesystem name")
> Fixes: 2b60c0ecedf8 ("IMA: Read keyrings= option from the IMA policy")
> Signed-off-by: Tyler Hicks <tyhicks@...ux.microsoft.com>

Thanks!  Thinking about it some more.  It makes more sense to define
ima_free_rule() here in this patch.

Mimi

> ---
>  security/integrity/ima/ima_policy.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 1320333201c6..94ca3b8abb69 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -1431,15 +1431,11 @@ ssize_t ima_parse_add_rule(char *rule)
>  void ima_delete_rules(void)
>  {
>  	struct ima_rule_entry *entry, *tmp;
> -	int i;
>  
>  	temp_ima_appraise = 0;
>  	list_for_each_entry_safe(entry, tmp, &ima_temp_rules, list) {
> -		for (i = 0; i < MAX_LSM_RULES; i++)
> -			kfree(entry->lsm[i].args_p);
> -
>  		list_del(&entry->list);
> -		kfree(entry);
> +		ima_free_rule(entry);
>  	}
>  }
>