Revert "[SCSI] Retrieve the Caching mode page"

commit 3dea642afd9187728d119fce5c82a7ed9faa9b6a upstream.

This reverts commit 24d720b726c1a85f1962831ac30ad4d2ef8276b1.

Previously we thought there was little possibility that devices would
crash with this, but some have been found.

Reported-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Luben Tuikov <ltuikov@yahoo.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 16 insertions, 47 deletions

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index e56730214c05..a63b94c0fba6 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1910,14 +1910,10 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
 	int old_rcd = sdkp->RCD;
 	int old_dpofua = sdkp->DPOFUA;
 
-	if (sdp->skip_ms_page_8) {
-		if (sdp->type == TYPE_RBC)
-			goto defaults;
-		else {
-			modepage = 0x3F;
-			dbd = 0;
-		}
-	} else if (sdp->type == TYPE_RBC) {
+	if (sdp->skip_ms_page_8)
+		goto defaults;
+
+	if (sdp->type == TYPE_RBC) {
 		modepage = 6;
 		dbd = 8;
 	} else {
@@ -1945,11 +1941,13 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
 	 */
 	if (len < 3)
 		goto bad_sense;
-	else if (len > SD_BUF_SIZE) {
-		sd_printk(KERN_NOTICE, sdkp, "Truncating mode parameter "
-			  "data from %d to %d bytes\n", len, SD_BUF_SIZE);
-		len = SD_BUF_SIZE;
-	}
+	if (len > 20)
+		len = 20;
+
+	/* Take headers and block descriptors into account */
+	len += data.header_length + data.block_descriptor_length;
+	if (len > SD_BUF_SIZE)
+		goto bad_sense;
 
 	/* Get the data */
 	res = sd_do_mode_sense(sdp, dbd, modepage, buffer, len, &data, &sshdr);
@@ -1957,45 +1955,16 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
 	if (scsi_status_is_good(res)) {
 		int offset = data.header_length + data.block_descriptor_length;
 
-		while (offset < len) {
-			u8 page_code = buffer[offset] & 0x3F;
-			u8 spf       = buffer[offset] & 0x40;
-
-			if (page_code == 8 || page_code == 6) {
-				/* We're interested only in the first 3 bytes.
-				 */
-				if (len - offset <= 2) {
-					sd_printk(KERN_ERR, sdkp, "Incomplete "
-						  "mode parameter data\n");
-					goto defaults;
-				} else {
-					modepage = page_code;
-					goto Page_found;
-				}
-			} else {
-				/* Go to the next page */
-				if (spf && len - offset > 3)
-					offset += 4 + (buffer[offset+2] << 8) +
-						buffer[offset+3];
-				else if (!spf && len - offset > 1)
-					offset += 2 + buffer[offset+1];
-				else {
-					sd_printk(KERN_ERR, sdkp, "Incomplete "
-						  "mode parameter data\n");
-					goto defaults;
-				}
-			}
+		if (offset >= SD_BUF_SIZE - 2) {
+			sd_printk(KERN_ERR, sdkp, "Malformed MODE SENSE response\n");
+			goto defaults;
 		}
 
-		if (modepage == 0x3F) {
-			sd_printk(KERN_ERR, sdkp, "No Caching mode page "
-				  "present\n");
-			goto defaults;
-		} else if ((buffer[offset] & 0x3f) != modepage) {
+		if ((buffer[offset] & 0x3f) != modepage) {
 			sd_printk(KERN_ERR, sdkp, "Got wrong page\n");
 			goto defaults;
 		}
-	Page_found:
+
 		if (modepage == 8) {
 			sdkp->WCE = ((buffer[offset + 2] & 0x04) != 0);
 			sdkp->RCD = ((buffer[offset + 2] & 0x01) != 0);