linux-hardening - Re: [PATCH net 1/2] iavf: Fix use-after-free in free

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Date:   Tue, 18 Apr 2023 18:02:39 +0200
From:   Michal Kubiak <michal.kubiak@...el.com>
To:     Ding Hui <dinghui@...gfor.com.cn>
CC:     <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <intel-wired-lan@...ts.osuosl.org>,
        <jesse.brandeburg@...el.com>, <anthony.l.nguyen@...el.com>,
        <keescook@...omium.org>, <grzegorzx.szczurek@...el.com>,
        <mateusz.palczewski@...el.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-hardening@...r.kernel.org>,
        "Donglin Peng" <pengdonglin@...gfor.com.cn>,
        Huang Cun <huangcun@...gfor.com.cn>
Subject: Re: [PATCH net 1/2] iavf: Fix use-after-free in free_netdev

On Sat, Apr 08, 2023 at 10:00:29PM +0800, Ding Hui wrote:
> We do netif_napi_add() for all allocated q_vectors[], but potentially
> do netif_napi_del() for part of them, then kfree q_vectors and lefted
> invalid pointers at dev->napi_list.
> 
> If num_active_queues is changed to less than allocated q_vectors[] by
> by unexpected, when iavf_remove, we might see UAF in free_netdev like this:

Nitpick: the word "by" is accidentally doubled.

Also, I would recommend to add a description of reproduction steps (most
preferably a script or a command sequence) which triggers such an error
reported by KASAN.

> 
> [ 4093.900222] ==================================================================
> [ 4093.900230] BUG: KASAN: use-after-free in free_netdev+0x308/0x390
> [ 4093.900232] Read of size 8 at addr ffff88b4dc145640 by task test-iavf-1.sh/6699
> [ 4093.900233]
> [ 4093.900236] CPU: 10 PID: 6699 Comm: test-iavf-1.sh Kdump: loaded Tainted: G           O     --------- -t - 4.18.0 #1
> [ 4093.900238] Hardware name: Powerleader PR2008AL/H12DSi-N6, BIOS 2.0 04/09/2021
> [ 4093.900239] Call Trace:
> [ 4093.900244]  dump_stack+0x71/0xab
> [ 4093.900249]  print_address_description+0x6b/0x290
> [ 4093.900251]  ? free_netdev+0x308/0x390
> [ 4093.900252]  kasan_report+0x14a/0x2b0
> [ 4093.900254]  free_netdev+0x308/0x390
> [ 4093.900261]  iavf_remove+0x825/0xd20 [iavf]
> [ 4093.900265]  pci_device_remove+0xa8/0x1f0
> [ 4093.900268]  device_release_driver_internal+0x1c6/0x460
> [ 4093.900271]  pci_stop_bus_device+0x101/0x150
> [ 4093.900273]  pci_stop_and_remove_bus_device+0xe/0x20
> [ 4093.900275]  pci_iov_remove_virtfn+0x187/0x420
> [ 4093.900277]  ? pci_iov_add_virtfn+0xe10/0xe10
> [ 4093.900278]  ? pci_get_subsys+0x90/0x90
> [ 4093.900280]  sriov_disable+0xed/0x3e0
> [ 4093.900282]  ? bus_find_device+0x12d/0x1a0
> [ 4093.900290]  i40e_free_vfs+0x754/0x1210 [i40e]
> [ 4093.900298]  ? i40e_reset_all_vfs+0x880/0x880 [i40e]
> [ 4093.900299]  ? pci_get_device+0x7c/0x90
> [ 4093.900300]  ? pci_get_subsys+0x90/0x90
> [ 4093.900306]  ? pci_vfs_assigned.part.7+0x144/0x210
> [ 4093.900309]  ? __mutex_lock_slowpath+0x10/0x10
> [ 4093.900315]  i40e_pci_sriov_configure+0x1fa/0x2e0 [i40e]
> [ 4093.900318]  sriov_numvfs_store+0x214/0x290
> [ 4093.900320]  ? sriov_totalvfs_show+0x30/0x30
> [ 4093.900321]  ? __mutex_lock_slowpath+0x10/0x10
> [ 4093.900323]  ? __check_object_size+0x15a/0x350
> [ 4093.900326]  kernfs_fop_write+0x280/0x3f0
> [ 4093.900329]  vfs_write+0x145/0x440
> [ 4093.900330]  ksys_write+0xab/0x160
> [ 4093.900332]  ? __ia32_sys_read+0xb0/0xb0
> [ 4093.900334]  ? fput_many+0x1a/0x120
> [ 4093.900335]  ? filp_close+0xf0/0x130
> [ 4093.900338]  do_syscall_64+0xa0/0x370
> [ 4093.900339]  ? page_fault+0x8/0x30
> [ 4093.900341]  entry_SYSCALL_64_after_hwframe+0x65/0xca
> [ 4093.900357] RIP: 0033:0x7f16ad4d22c0
> ---
>  drivers/net/ethernet/intel/iavf/iavf_main.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c b/drivers/net/ethernet/intel/iavf/iavf_main.c
> index 095201e83c9d..a57e3425f960 100644
> --- a/drivers/net/ethernet/intel/iavf/iavf_main.c
> +++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
> @@ -1849,19 +1849,15 @@ static int iavf_alloc_q_vectors(struct iavf_adapter *adapter)
>  static void iavf_free_q_vectors(struct iavf_adapter *adapter)
>  {
>  	int q_idx, num_q_vectors;
> -	int napi_vectors;
>  
>  	if (!adapter->q_vectors)
>  		return;
>  
>  	num_q_vectors = adapter->num_msix_vectors - NONQ_VECS;
> -	napi_vectors = adapter->num_active_queues;
>  
>  	for (q_idx = 0; q_idx < num_q_vectors; q_idx++) {
>  		struct iavf_q_vector *q_vector = &adapter->q_vectors[q_idx];
> -
> -		if (q_idx < napi_vectors)
> -			netif_napi_del(&q_vector->napi);
> +		netif_napi_del(&q_vector->napi);
>  	}
>  	kfree(adapter->q_vectors);
>  	adapter->q_vectors = NULL;

The fix looks correct to me.
We actually call "netif_napi_add()" for all allocated q_vectors unconditionally
in "iavf_alloc_q_vectors()").

Thanks,
Michal

> -- 
> 2.17.1
>