Re: [PATCH net] net: hns3: Fix for out-of-bounds access when setting pfc back pressure

[John Garry]

On 01/11/2018 12:12, Yunsheng Lin wrote:
> The vport should be initialized to hdev->vport for each bp group,
> otherwise it will cause out-of-bounds access and bp setting not
> correct problem.
>
> [   35.254124] BUG: KASAN: slab-out-of-bounds in hclge_pause_setup_hw+0x2a0/0x3f8 [hclge]
> [   35.254126] Read of size 2 at addr ffff803b6651581a by task kworker/0:1/14
>
> [   35.254132] CPU: 0 PID: 14 Comm: kworker/0:1 Not tainted 4.19.0-rc7-hulk+ #85
> [   35.254133] Hardware name: Huawei D06/D06, BIOS Hisilicon D06 UEFI RC0 - B052 (V0.52) 09/14/2018
> [   35.254141] Workqueue: events work_for_cpu_fn
> [   35.254144] Call trace:
> [   35.254147]  dump_backtrace+0x0/0x2f0
> [   35.254149]  show_stack+0x24/0x30
> [   35.254154]  dump_stack+0x110/0x184
> [   35.254157]  print_address_description+0x168/0x2b0
> [   35.254160]  kasan_report+0x184/0x310
> [   35.254162]  __asan_load2+0x7c/0xa0
> [   35.254170]  hclge_pause_setup_hw+0x2a0/0x3f8 [hclge]
> [   35.254177]  hclge_tm_init_hw+0x794/0x9f0 [hclge]
> [   35.254184]  hclge_tm_schd_init+0x48/0x58 [hclge]
> [   35.254191]  hclge_init_ae_dev+0x778/0x1168 [hclge]
> [   35.254196]  hnae3_register_ae_dev+0x14c/0x298 [hnae3]
> [   35.254206]  hns3_probe+0x88/0xa8 [hns3]
> [   35.254210]  local_pci_probe+0x7c/0xf0
> [   35.254212]  work_for_cpu_fn+0x34/0x50
> [   35.254214]  process_one_work+0x4d4/0xa38
> [   35.254216]  worker_thread+0x55c/0x8d8
> [   35.254219]  kthread+0x1b0/0x1b8
> [   35.254222]  ret_from_fork+0x10/0x1c
>
> [   35.254224] The buggy address belongs to the page:
> [   35.254228] page:ffff7e00ed994400 count:1 mapcount:0 mapping:0000000000000000 index:0x0 compound_mapcount: 0
> [   35.273835] flags: 0xfffff8000008000(head)
> [   35.282007] raw: 0fffff8000008000 dead000000000100 dead000000000200 0000000000000000
> [   35.282010] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
> [   35.282012] page dumped because: kasan: bad access detected
>
> [   35.282014] Memory state around the buggy address:
> [   35.282017]  ffff803b66515700: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
> [   35.282019]  ffff803b66515780: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
> [   35.282021] >ffff803b66515800: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
> [   35.282022]                             ^
> [   35.282024]  ffff803b66515880: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
> [   35.282026]  ffff803b66515900: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
> [   35.282028] ==================================================================
> [   35.282029] Disabling lock debugging due to kernel taint
> [   35.282747] hclge driver initialization finished.
>
> Fixes: 67bf2541f4b9 ("net: hns3: Fixes the back pressure setting when sriov is enabled")
> Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
> ---
>  drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c
> index aa5cb98..0c9c6ae 100644
> --- a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c
> +++ b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c
> @@ -1168,11 +1168,12 @@ static int hclge_pfc_setup_hw(struct hclge_dev *hdev)
>   */
>  static int hclge_bp_setup_hw(struct hclge_dev *hdev, u8 tc)
>  {
> -	struct hclge_vport *vport = hdev->vport;
>  	u32 i, k, qs_bitmap;
>  	int ret;
>
>  	for (i = 0; i < HCLGE_BP_GRP_NUM; i++) {
> +		struct hclge_vport *vport = hdev->vport;
> +

It seems to me that the bug is fixed but the code is not much better.

Since variable vport is only referenced in the inner loop, I would 
define it there.

>  		qs_bitmap = 0;
>
>  		for (k = 0; k < hdev->num_alloc_vport; k++) {

static int hclge_bp_setup_hw(struct hclge_dev *hdev, u8 tc)
 {
-       struct hclge_vport *vport = hdev->vport;
-       u32 i, k, qs_bitmap;
-       int ret;
+       int ret, i;

        for (i = 0; i < HCLGE_BP_GRP_NUM; i++) {
-               qs_bitmap = 0;
+               u32 qs_bitmap = 0;
+               int k;

                for (k = 0; k < hdev->num_alloc_vport; k++) {
+                       struct hclge_vport *vport = &hdev->vport[k];
                        u16 qs_id = vport->qs_offset + tc;
                        u8 grp, sub_grp;

...

                        if (i == grp)
                                qs_bitmap |= (1 << sub_grp);
-
-                       vport++;


... so this seems better and safer, as you're explicitly limiting vport 
within bounds of hdev->num_alloc_vport.