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Date:   Thu, 8 Apr 2021 17:38:22 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Liam Howlett <liam.howlett@oracle.com>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        "linux-m68k@lists.linux-m68k.org" <linux-m68k@lists.linux-m68k.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        Michel Lespinasse <walken@google.com>
Subject: Re: [PATCH] arch/m68k/kernel/sys_m68k: Add missing mmap_read_lock()
 to sys_cacheflush()
Message-ID: <20210408163822.GP2531743@casper.infradead.org>
References: <20210407200032.764445-1-Liam.Howlett@Oracle.com>
 <20210408163400.bcsmojb4ug7nnzwt@revolver>
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On Thu, Apr 08, 2021 at 04:34:20PM +0000, Liam Howlett wrote:
> When the superuser flushes the entire cache, the mmap_read_lock() is not
> taken, but mmap_read_unlock() is called.  Add the missing
> mmap_read_lock() call.
> 
> Fixes: cd2567b6850b (m68k: call find_vma with the mmap_sem held in
> sys_cacheflush())
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>

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

Although if it's been broken since 2014, maybe the ability of the
superuser to flush the entire cache is not needed any more and can
be removed?