Hi Ewan
Thanks for your kindly response.
On 3/26/19 9:06 PM, Ewan D. Milne wrote:
> See below.
>
> On Mon, 2019-03-25 at 15:40 +0800, Jianchao Wang wrote:
>> We have some places with risk of accessing out of bound of the
>> buffer allocated from slab, even it could corrupt the memory.
>>
>> Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx>
>> ---
>> drivers/scsi/ses.c | 27 ++++++++++++++++++++++-----
>> 1 file changed, 22 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c
>> index 0fc3922..42e6a1f 100644
>> --- a/drivers/scsi/ses.c
>> +++ b/drivers/scsi/ses.c
>> @@ -520,6 +520,7 @@ static void ses_enclosure_data_process(struct enclosure_device *edev,
>> struct ses_device *ses_dev = edev->scratch;
>> int types = ses_dev->page1_num_types;
>> unsigned char *hdr_buf = kzalloc(INIT_ALLOC_SIZE, GFP_KERNEL);
>> + unsigned char *page1_end = ses_dev->page1 + ses_dev->page1_len;
>>
>> if (!hdr_buf)
>> goto simple_populate;
>> @@ -556,6 +557,11 @@ static void ses_enclosure_data_process(struct enclosure_device *edev,
>> type_ptr = ses_dev->page1_types;
>> components = 0;
>> for (i = 0; i < types; i++, type_ptr += 4) {
>> + if (type_ptr > page1_end - 2) {
>
> I think "if (type_ptr + 1 >= page1_end)" would be more consistent.
Yes, indeed.
>
>> + sdev_printk(KERN_ERR, sdev, "Access out of bound of page1"
>> + "%p page1_end %p\n", page1_end, type_ptr);
>
> This message is not helpful for someone with a device reporting
> invalid enclosure data. It should be more generic, like
> "Enclosure data too short" or "invalid" or something. And, the
> actual pointer values are irrelevant, it all depends upon the
> contents of the buffer.
>
>> + break;
>> + }
>> for (j = 0; j < type_ptr[1]; j++) {
>> char *name = NULL;
>> struct enclosure_component *ecomp;
>> @@ -566,10 +572,15 @@ static void ses_enclosure_data_process(struct enclosure_device *edev,
>> } else {
>> len = (desc_ptr[2] << 8) + desc_ptr[3];
>> desc_ptr += 4;
>> - /* Add trailing zero - pushes into
>> - * reserved space */
>> - desc_ptr[len] = '\0';
>> - name = desc_ptr;
>> + if (desc_ptr + len >= buf + page7_len) {
>> + desc_ptr = NULL;
>> + } else {
>> +
>> + /* Add trailing zero - pushes into
>> + * reserved space */
>> + desc_ptr[len] = '\0';
>> + name = desc_ptr;
>> + }
>> }
>> }
>> if (type_ptr[0] == ENCLOSURE_COMPONENT_DEVICE ||
>> @@ -693,7 +704,13 @@ static int ses_intf_add(struct device *cdev,
>> /* begin at the enclosure descriptor */
>> type_ptr = buf + 8;
>> /* skip all the enclosure descriptors */
>> - for (i = 0; i < num_enclosures && type_ptr < buf + len; i++) {
>> + for (i = 0; i < num_enclosures; i++) {
>> + if (type_ptr >= buf + len) {
>> + sdev_printk(KERN_ERR, sdev, "Overflow the buf len = %d\n", len);
>
> See above, the message is unhelpful. The actual problem is that
> the Enclosure data is too short or invalid.
Yes, maybe we should dump all of the information of the page1 here.
>
>> + err = -EINVAL;
>> + goto err_free;
>> + }
>> +
>> types += type_ptr[2];
>> type_ptr += type_ptr[3] + 4;
>> }
>
> This will still potentially leave type_ptr past the end of the
> buffer in the subsequent code, though, right?
Yes, type_ptr[3] is accessing type_ptr + 3 which has be beyond our checking point.
>
> This might fix the problem for your malfunctioning device, but
> does not look like it would handle the general case.
>
Actually, I really don't know much about this ses driver. I sent out this bad patch
because I want to push things forward as there is a serious issue on our customer
side.
Thanks
Jianchao
