[uml-devel] Re: [patch 1/1] Fix malloc-use-vmalloc

[BlaisorBlade <blaisorblade_spam@yahoo.it>]

Alle 19:57, martedì 13 luglio 2004, Jeff Dike ha scritto:

> This isn't exactly right.  In the case that a buffer was allocated by
> kmalloc (through malloc), but freed when the system is coming down, and
> kmalloc is no longer operating, then you just want to do nothing. It would
> be very bad to try to free it using libc free.
>
> So, what I did is this:
>
> 	if((addr >= uml_physmem) && (addr <= high_physmem)){
> 		if(CAN_KMALLOC())
> 			kfree(ptr);
> 	}
> 	else if((addr >= start_vm) && (addr <= end_vm)){
> 		if(CAN_KMALLOC())
> 			vfree(ptr);
> 	}
> 	else __real_free(ptr);

1) I think that the intervals don't include high_physmem and end_vm, so we 
should have addr < ... instead of addr <=.

2) Also, even worse, it seems ok until you read your comment. During the boot, 
if random values are in the vars (and it's so until kmalloc_ok is turned on) 
we can have malloc()ed memory thought of as kmalloc()ed or vmalloc()ed one, 
and then leaked.

3) Solution to 2): if I am right about thing #1, then it should be enough to 
set end_vm and high_physmem to 0 at startup (they are global vars, so it's 
already true), once there are the < instead of <=. And don't say in the 
comment that memory regions are not initialized.

Any comment? I need this to send the patch to Andrew Morton for 2.6-mm
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729




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