linux-kernel - Re: [PATCH] [v2] nvdimm-btt: fix several memleaks

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Message-ID: <657c82966e358_2947c22941a@iweiny-mobl.notmuch>
Date: Fri, 15 Dec 2023 08:45:10 -0800
From: Ira Weiny <ira.weiny@...el.com>
To: Ira Weiny <ira.weiny@...el.com>, Dinghao Liu <dinghao.liu@....edu.cn>
CC: Dan Williams <dan.j.williams@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>, Ira Weiny
	<ira.weiny@...el.com>, <nvdimm@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [v2] nvdimm-btt: fix several memleaks

Ira Weiny wrote:
> Dinghao Liu wrote:

[snip]

> >  
> > -static int btt_maplocks_init(struct arena_info *arena)
> > +static int btt_maplocks_init(struct device *dev, struct arena_info *arena)
> >  {
> >  	u32 i;
> >  
> > -	arena->map_locks = kcalloc(arena->nfree, sizeof(struct aligned_lock),
> > +	arena->map_locks = devm_kcalloc(dev, arena->nfree, sizeof(struct aligned_lock),
> >  				GFP_KERNEL);
> >  	if (!arena->map_locks)
> >  		return -ENOMEM;
> > @@ -805,9 +805,6 @@ static void free_arenas(struct btt *btt)
> >  
> >  	list_for_each_entry_safe(arena, next, &btt->arena_list, list) {
> >  		list_del(&arena->list);
> > -		kfree(arena->rtt);
> > -		kfree(arena->map_locks);
> > -		kfree(arena->freelist);
> 
> This does not quite work.
> 
> free_arenas() is used in the error paths of create_arenas() and
> discover_arenas().  In those cases devm_kfree() is probably a better way
> to clean up this.
> 
> However...
> 
> >  		debugfs_remove_recursive(arena->debugfs_dir);
> >  		kfree(arena);
> 
> Why can't arena be allocated with devm_*?
> 
> We need to change this up a bit more to handle the error path vs regular
> device shutdown free (automatic devm frees).

We might want to look at using no_free_ptr() in this code.  See this
patch[1] for an example of how to inhibit the cleanup and pass the pointer
on when the function succeeds.

[1] https://lore.kernel.org/all/170261791914.1714654.6447680285357545638.stgit@dwillia2-xfh.jf.intel.com/

Ira