[SCSI] sd name space exhaustion causes system hang

Following a site power outage which re-enabled all the ports on my FC
switches, my system subsequently booted with far too many luns!  I had
let it run hoping it would make multi-user.  It didn't.  :(  It hung solid
after exhausting the last sd device, sdzzz, and attempting to create sdaaaa
and beyond.  I was unable to get a dump.

Discovered using a 2.6.32.13 based system.

correct this by detecting when the last index is utilized and failing
the sd probe of the device.  Patch applies to scsi-misc-2.6.

Signed-off-by: Michael Reed <mdr@sgi.com>
Cc: Stable Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 0c4f89cfb7dc..50f1fe605303 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2288,11 +2288,10 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
         index = sdkp->index;
         dev = &sdp->sdev_gendev;
 
-        if (index < SD_MAX_DISKS) {
-                gd->major = sd_major((index & 0xf0) >> 4);
-                gd->first_minor = ((index & 0xf) << 4) | (index & 0xfff00);
-                gd->minors = SD_MINORS;
-        }
+        gd->major = sd_major((index & 0xf0) >> 4);
+        gd->first_minor = ((index & 0xf) << 4) | (index & 0xfff00);
+        gd->minors = SD_MINORS;
+
         gd->fops = &sd_fops;
         gd->private_data = &sdkp->driver;
         gd->queue = sdkp->device->request_queue;
@@ -2382,6 +2381,12 @@ static int sd_probe(struct device *dev)
         if (error)
                 goto out_put;
 
+        if (index >= SD_MAX_DISKS) {
+                error = -ENODEV;
+                sdev_printk(KERN_WARNING, sdp, "SCSI disk (sd) name space exhausted.\n");
+                goto out_free_index;
+        }
+
         error = sd_format_disk_name("sd", index, gd->disk_name, DISK_NAME_LEN);
         if (error)
                 goto out_free_index;