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Subject[2.4.19] [2.4.20-pre6] loop.c memory allocation & freeing problem
Date
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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°---------------------°----------------°------------------°--------------------°
--- 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;
}
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