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Subjectinquiry in scsi_scan.c
Got a new USB device and noticed some scsi silliness while playing with it.

A bug in scsi_scan.c is

sdev->inquiry = kmalloc(sdev->inquiry_len, GFP_ATOMIC);
memcpy(sdev->inquiry, inq_result, sdev->inquiry_len);
sdev->vendor = (char *) (sdev->inquiry + 8);
sdev->model = (char *) (sdev->inquiry + 16);
sdev->rev = (char *) (sdev->inquiry + 32);

since it happens that inquiry_len is short (in my case it is 5)
and the vendor/model/rev pointers are wild.
Catting /proc/scsi/scsi now yields random garbage.

I made a patch but hesitated between a small patch and a larger one.
Why do we have this malloced inquiry field? As far as I can see
nobody uses it. And the comment in scsi_add_lun() advises us
not to save the inquiry, precisely what we did until recently.
So, should this change from 2.5.11 be reverted?

Andries


[My present scsi_scan.c differes quite a lot from a stock one.
Already fixed the scsi_check_id_size() some time ago.
Below some diff fragments from today.]

+/*
+ * Do an INQUIRY with given length (minimum 5, maximum 255).
+ * Note: many devices react badly when given an unexpected length.
+ */
+static int
+scsi_do_inquiry(Scsi_Request *sreq, char *buffer, int len) {
+ Scsi_Device *sdev = sreq->sr_device;
+ unsigned char cmd[6];
+ int res;
+
+ SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO "scsi scan: INQUIRY (len %d) "
+ "to host %d channel %d id %d lun %d\n",
+ len, sdev->host->host_no, sdev->channel,
+ sdev->id, sdev->lun));
+
+ memset(cmd, 0, 6);
+ cmd[0] = INQUIRY;
+ cmd[4] = len;
+ sreq->sr_cmd_len = 0;
+ sreq->sr_data_direction = SCSI_DATA_READ;
+ memset(buffer, 0, len);
+
+ scsi_wait_req(sreq, (void *) cmd, (void *) buffer, len,
+ SCSI_TIMEOUT + 4 * HZ, 3);
+
+ res = sreq->sr_result;
+ SCSI_LOG_SCAN_BUS(3, printk(res ? KERN_INFO "scsi scan: "
+ "INQUIRY returned code 0x%x\n" :
+ KERN_INFO "scsi scan: INQUIRY OK\n", res));
+ return res;
+}

+/*
+ * The inquiry length is inq_result[4] + 5 unless overridden.
+ */
+static int
+valid_inquiry_lth(int bflags, unsigned char *inq_result) {
+ int len = ((bflags & BLIST_INQUIRY_36) ? 36 :
+ (bflags & BLIST_INQUIRY_58) ? 58 :
+ inq_result[4] + 5);
+ if (len > 255)
+ len = 36; /* sanity */
+ return len;
+}

Text in scsi_probe_lun(), including two reactions to comments:

static void
scsi_probe_lun(Scsi_Request *sreq, char *inq_result, int *bflags)
{
Scsi_Device *sdev = sreq->sr_device; /* a bit ugly */
unsigned char scsi_cmd[MAX_COMMAND_SIZE];
int res, possible_inq_resp_len;

/* first issue an inquiry with conservative alloc_length */
res = scsi_do_inquiry(sreq, inq_result, 36);

if (res) {
if ((driver_byte(res) & DRIVER_SENSE) != 0 &&
(sreq->sr_sense_buffer[2] & 0xf) == UNIT_ATTENTION &&
sreq->sr_sense_buffer[12] == 0x28 &&
sreq->sr_sense_buffer[13] == 0) {
/* not-ready to ready transition - good */
/* dpg: bogus? INQUIRY never returns UNIT_ATTENTION */
/* aeb: seen with an USB CF card reader */
} else
/*
* assume no peripheral if any other sort of error
*/
return;
}

/*
* Get any flags for this device.
*
* Some devices return only 5 bytes for an INQUIRY, but the memset
* in scsi_do_inquiry makes sure that scsi_get_device_flags() gets
* well-defined arguments.
*/
*bflags = scsi_get_device_flags(&inq_result[8], &inq_result[16]);

possible_inq_resp_len = valid_inquiry_lth(*bflags, inq_result);

if (possible_inq_resp_len > 36) { /* do additional INQUIRY */
res = scsi_do_inquiry(sreq, inq_result, possible_inq_resp_len);
if (res)
return;

/*
* The INQUIRY can change, this means the length can change.
*/
possible_inq_resp_len = valid_inquiry_lth(*bflags, inq_result);
}

sdev->inquiry_len = possible_inq_resp_len;

/*
* Abort if the response length is less than 36?
* No, some USB devices just produce the minimal 5-byte INQUIRY.
*
* ...
*/


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