linux-kernel - Re: [PATCH 1/2] mm/vmalloc: Add a safer version of find_vm

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Message-ID: <ZO8xHT5HUDTSVUai@casper.infradead.org>
Date:   Wed, 30 Aug 2023 13:07:57 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Zhen Lei <thunder.leizhen@...weicloud.com>,
        "Paul E . McKenney" <paulmck@...nel.org>, rcu@...r.kernel.org,
        Zqiang <qiang.zhang1211@...il.com>, linux-mm@...ck.org
Subject: Re: [PATCH 1/2] mm/vmalloc: Add a safer version of find_vm_area()
 for debug

On Wed, Aug 30, 2023 at 11:03:59AM +0000, Joel Fernandes (Google) wrote:
> It is unsafe to dump vmalloc area information when trying to do so from
> some contexts. Add a safer trylock version of the same function to do a
> best-effort VMA finding and use it from vmalloc_dump_obj().
> 
> Reported-by: Zhen Lei <thunder.leizhen@...weicloud.com>
> Cc: Paul E. McKenney <paulmck@...nel.org>
> Cc: rcu@...r.kernel.org
> Cc: Zqiang <qiang.zhang1211@...il.com>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>

Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>

I once started writing something similar, but got distracted and the
immediate problem got solved a different way.

It does make me wonder if we couldn't make this tree RCU-safe, but
that's obviously a much larger job.