linux-kernel - Re: [PATCH][next] mm/vmalloc: Fix read of pointer area after it has been free'd

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Message-ID: <20210329174029.GA457@pc638.lan>
Date:   Mon, 29 Mar 2021 19:40:29 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Colin King <colin.king@...onical.com>
Cc:     Colin King <colin.king@...onical.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Nicholas Piggin <npiggin@...il.com>, linux-mm@...ck.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] mm/vmalloc: Fix read of pointer area after it has
 been free'd

On Mon, Mar 29, 2021 at 06:14:34PM +0100, Matthew Wilcox wrote:
> On Mon, Mar 29, 2021 at 06:07:30PM +0100, Colin King wrote:
> > From: Colin Ian King <colin.king@...onical.com>
> > 
> > Currently the memory pointed to by area is being freed by the
> > free_vm_area call and then area->nr_pages is referencing the
> > free'd object. Fix this swapping the order of the warn_alloc
> > message and the free.
> > 
> > Addresses-Coverity: ("Read from pointer after free")
> > Fixes: 014ccf9b888d ("mm/vmalloc: improve allocation failure error messages")
> 
> i don't have this git sha.  if this is -next, the sha ids aren't stable
> and shouldn't be referenced in commit logs, because these fixes should
> just be squashed into the not-yet-upstream commits.
> 
> > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> > ---
> >  mm/vmalloc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index b73e4e715e0d..7936405749e4 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2790,11 +2790,11 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> >  	}
> >  
> >  	if (!pages) {
> > -		free_vm_area(area);
> >  		warn_alloc(gfp_mask, NULL,
> >  			   "vmalloc size %lu allocation failure: "
> >  			   "page array size %lu allocation failed",
> >  			   area->nr_pages * PAGE_SIZE, array_size);
> > +		free_vm_area(area);
> >  		return NULL;
> 
> this fix looks right to me.
> 
That is from the linux-next. Same to me.

Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>

--
Vlad Rezki