linux-kernel - Re: [PATCH v9 08/69] mm: start tracking VMAs with maple tree

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Message-ID: <20220512175041.7dfrtpupnomtvxo2@revolver>
Date:   Thu, 12 May 2022 17:50:58 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Qian Cai <quic_qiancai@...cinc.com>
CC:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v9 08/69] mm: start tracking VMAs with maple tree

* Qian Cai <quic_qiancai@...cinc.com> [220512 13:01]:
> On Wed, May 04, 2022 at 01:07:52AM +0000, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> > 
> > Start tracking the VMAs with the new maple tree structure in parallel with
> > the rb_tree.  Add debug and trace events for maple tree operations and
> > duplicate the rb_tree that is created on forks into the maple tree.
> > 
> > The maple tree is added to the mm_struct including the mm_init struct,
> > added support in required mm/mmap functions, added tracking in kernel/fork
> > for process forking, and used to find the unmapped_area and checked
> > against what the rbtree finds.
> > 
> > This also moves the mmap_lock() in exit_mmap() since the oom reaper call
> > does walk the VMAs.  Otherwise lockdep will be unhappy if oom happens.
> > 
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ...
> > @@ -2479,9 +2693,14 @@ int expand_downwards(struct vm_area_struct *vma,
> >  			return -ENOMEM;
> >  	}
> >  
> > +	if (mas_preallocate(&mas, vma, GFP_KERNEL))
> 
> We have thousands of leaks reports here from kmemleak while running some
> syscall fuzzers on today's linux-next tree.

Thanks for the report.  Yes, this is mine.  I am testing a fix now.

> 
> unreferenced object 0xffff0803c0063d00 (size 256):
>   comm "trinity-c25", pid 177739, jiffies 4297781293 (age 354.988s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>      slab_post_alloc_hook
>      kmem_cache_alloc_bulk
>      mas_alloc_nodes
>      mas_preallocate
>      mas_preallocate at lib/maple_tree.c:5579
>      expand_downwards
>      expand_downwards at mm/mmap.c:2094
>      expand_stack
>      do_page_fault
>      do_translation_fault
>      do_mem_abort
>      el1_abort
>      el1h_64_sync_handler
>      el1h_64_sync
>      handle_futex_death
>      exit_robust_list
>      futex_exit_release
>      exit_mm_release
> 
> > +		return -ENOMEM;
> > +
> >  	/* We must make sure the anon_vma is allocated. */
> > -	if (unlikely(anon_vma_prepare(vma)))
> > +	if (unlikely(anon_vma_prepare(vma))) {
> > +		mas_destroy(&mas);
> >  		return -ENOMEM;
> > +	}
> >  
> >  	/*
> >  	 * vma->vm_start/vm_end cannot change under us because the caller