linux-kernel - Re: [PATCH] apparmor: free the allocated pdb objects

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Date:   Tue, 28 Nov 2023 06:29:38 -0800
From:   John Johansen <john.johansen@...onical.com>
To:     Fedor Pchelkin <pchelkin@...ras.ru>
Cc:     Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Georgia Garcia <georgia.garcia@...onical.com>,
        apparmor@...ts.ubuntu.com, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        lvc-project@...uxtesting.org
Subject: Re: [PATCH] apparmor: free the allocated pdb objects

On 11/27/23 09:59, Fedor Pchelkin wrote:
> policy_db objects are allocated with kzalloc() inside aa_alloc_pdb() and
> are not cleared in the corresponding aa_free_pdb() function causing leak:
> 
> unreferenced object 0xffff88801f0a1400 (size 192):
>    comm "apparmor_parser", pid 1247, jiffies 4295122827 (age 2306.399s)
>    hex dump (first 32 bytes):
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>    backtrace:
>      [<ffffffff81ddc612>] __kmem_cache_alloc_node+0x1e2/0x2d0
>      [<ffffffff81c47c55>] kmalloc_trace+0x25/0xc0
>      [<ffffffff83eb9a12>] aa_alloc_pdb+0x82/0x140
>      [<ffffffff83ec4077>] unpack_pdb+0xc7/0x2700
>      [<ffffffff83ec6b10>] unpack_profile+0x450/0x4960
>      [<ffffffff83ecc129>] aa_unpack+0x309/0x15e0
>      [<ffffffff83ebdb23>] aa_replace_profiles+0x213/0x33c0
>      [<ffffffff83e8d341>] policy_update+0x261/0x370
>      [<ffffffff83e8d66e>] profile_replace+0x20e/0x2a0
>      [<ffffffff81eadfaf>] vfs_write+0x2af/0xe00
>      [<ffffffff81eaf4c6>] ksys_write+0x126/0x250
>      [<ffffffff890fa0b6>] do_syscall_64+0x46/0xf0
>      [<ffffffff892000ea>] entry_SYSCALL_64_after_hwframe+0x6e/0x76
> 
> Free the pdbs inside aa_free_pdb(). While at it, rename the variable
> representing an aa_policydb object to make the function more unified with
> aa_pdb_free_kref() and aa_alloc_pdb().
> 
> Found by Linux Verification Center (linuxtesting.org).
> 
> Fixes: 98b824ff8984 ("apparmor: refcount the pdb")
> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>

ouch, lgtm, I am going to pull this into my tree and throw some testing
on this asap

Acked-by: John Johansen <john.johansen@...onical.com>

> ---
>   security/apparmor/policy.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/security/apparmor/policy.c b/security/apparmor/policy.c
> index ed4c9803c8fa..957654d253dd 100644
> --- a/security/apparmor/policy.c
> +++ b/security/apparmor/policy.c
> @@ -99,13 +99,14 @@ const char *const aa_profile_mode_names[] = {
>   };
>   
>   
> -static void aa_free_pdb(struct aa_policydb *policy)
> +static void aa_free_pdb(struct aa_policydb *pdb)
>   {
> -	if (policy) {
> -		aa_put_dfa(policy->dfa);
> -		if (policy->perms)
> -			kvfree(policy->perms);
> -		aa_free_str_table(&policy->trans);
> +	if (pdb) {
> +		aa_put_dfa(pdb->dfa);
> +		if (pdb->perms)
> +			kvfree(pdb->perms);
> +		aa_free_str_table(&pdb->trans);
> +		kfree(pdb);
>   	}
>   }
>