[2.4.19] [2.4.20-pre6] loop.c memory allocation & freeing problem

[2.4.19] [2.4.20-pre6] loop.c memory allocation & freeing problem

[Yann E. MORIN]

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Hi All!

I think I've spotted a bug in the initialisation procedure in the loop driver,
@line 1027-1060, when there is allocation failure:

----BEGIN CODE----
        loop_dev = kmalloc(max_loop * sizeof(struct loop_device), GFP_KERNEL);
        if (!loop_dev)
                return -ENOMEM;

        loop_sizes = kmalloc(max_loop * sizeof(int), GFP_KERNEL);
        if (!loop_sizes)
                goto out_sizes;

        loop_blksizes = kmalloc(max_loop * sizeof(int), GFP_KERNEL);
        if (!loop_blksizes)
                goto out_blksizes;

[...SNIP...]

out_sizes:
        kfree(loop_dev);
out_blksizes:
        kfree(loop_sizes);
----END CODE----

Two problems arise there:
1) Should allocation of loop_sizes fail, we'll try to free loop_sizes that
   was NOT allocated (no problem because kfree does not free a NULL pointer).
   But not very clean...

2) Should allocation of loop_blksizes fail, loop_dev will NOT be freed.
   That one looks more problematic.

Am I wrong? Have I missed something? Anyway it's been there for ages, I
suppose.

Patch is very straigthforward, and is attached : swap the last 2 pairs of
lines, so that out_blksizes is before out_sizes, and kfree(loop_sizes is
before kfree(loop_dev).

Please CC: answers and comments as I'm no longer subscribed.

Cheers,
Yann.

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[-- Attachment #2: loop.c.diff --]
[-- Type: text/plain, Size: 346 bytes --]

--- loop.c.old	Thu Sep 12 21:19:40 2002
+++ loop.c	Thu Sep 12 21:19:56 2002
@@ -1054,10 +1054,10 @@
 	printk(KERN_INFO "loop: loaded (max %d devices)\n", max_loop);
 	return 0;
 
-out_sizes:
-	kfree(loop_dev);
 out_blksizes:
 	kfree(loop_sizes);
+out_sizes:
+	kfree(loop_dev);
 	printk(KERN_ERR "loop: ran out of memory\n");
 	return -ENOMEM;
 }