scsi: sd: Fix VPD page 0xb7 length check

sd_read_block_limits_ext() currently assumes that vpd->len excludes the
size of the page header. However, vpd->len describes the size of the entire
VPD page, therefore the sanity check is incorrect.

In practice this is not really a problem since we don't attach VPD
pages unless they actually report data trailing the header. But fix
the length check regardless.

This issue was identified by Wukong-Agent (formerly Tencent Woodpecker), a
code security AI agent, through static code analysis.

[mkp: rewrote patch description]

Signed-off-by: jackysliu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Fixes: 96b171d ("scsi: core: Query the Block Limits Extension VPD page")
Signed-off-by: Martin K. Petersen <[email protected]>

Author: forsaken641

drivers/scsi/sd.c

@@ -3384,7 +3384,7 @@ static void sd_read_block_limits_ext(struct scsi_disk *sdkp)
 
 	rcu_read_lock();
 	vpd = rcu_dereference(sdkp->device->vpd_pgb7);
-	if (vpd && vpd->len >= 2)
+	if (vpd && vpd->len >= 6)
 		sdkp->rscs = vpd->data[5] & 1;
 	rcu_read_unlock();
 }