[Cluster-devel] [PATCH] fs, dlm: Don't leak, don't do pointless NULL checks and use kzalloc

[Cluster-devel] [PATCH] fs, dlm: Don't leak, don't do pointless NULL checks and use kzalloc

[David Teigland]

On Wed, Jun 29, 2011 at 11:09:27PM +0200, Jesper Juhl wrote:
> In fs/dlm/lock.c in the dlm_scan_waiters() function there are 3 small
> issues:
> 
> 1) first time through the loop we allocate memory for 'warned', if we
> then (in the loop) don't take the "if (!warned)" path and loop again,
> the second time through the loop we'll allocate memory again and store
> it to 'warned' without freeing the previous allocation - this leaks
> memory.

I don't think so; num_nodes won't be set to zero.

> 2) There's no need to test the return value of the allocation and do a
> memset if is succeedes. Just use kzalloc() to obtain zeroed memory.

fine

> 3) Since kfree() handles NULL pointers gracefully, the test of
> 'warned' against NULL before the kfree() after the loop is completely
> pointless. Remove it.

fine

ack if you want to push those two out yourself.
Dave

[Cluster-devel] [PATCH] fs, dlm: Don't leak, don't do pointless NULL checks and use kzalloc

[David Teigland]

On Wed, Jun 29, 2011 at 11:51:00PM +0200, Jesper Juhl wrote:
> > I don't think so; num_nodes won't be set to zero.
> 
> Hmm. How so?  Maybe I'm missing something obvious, but;
> num_nodes is initialized to zero at the beginning of the function, which 
> means that we'll definately do the first allocation in the loop.

Zero is meant to mean "first time through the loop".

> We then set num_nodes equal to ls->ls_num_nodes - what guarantees that 
> this will not be zero so we won't do a second allocation (and leak) the 
> second time through the loop?

That's just the nature of a lockspace, I guess -- it doesn't make sense or
exist without nodes in it.  I doubt any of the dlm code would work if that
weren't true.

Dave