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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
	kirill.shutemov@linux.intel.com, riel@redhat.com, mhocko@suse.cz,
	oleg@redhat.com, sasha.levin@oracle.com,
	gang.chen.5i5j@gmail.com, pfeiner@google.com,
	aarcange@redhat.com, vishnu.ps@samsung.com, linux-mm@kvack.org,
	glider@google.com, kcc@google.com, andreyknvl@google.com,
	ktsan@googlegroups.com, paulmck@linux.vnet.ibm.com
Subject: Re: [PATCH] fs: fix data race on mnt.mnt_flags
Date: Mon, 21 Sep 2015 17:06:15 +0300	[thread overview]
Message-ID: <20150921140615.GA30755@node.dhcp.inet.fi> (raw)
In-Reply-To: <1442837807-70839-1-git-send-email-dvyukov@google.com>

On Mon, Sep 21, 2015 at 02:16:47PM +0200, Dmitry Vyukov wrote:
> do_remount() does:
> 
> mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
> mnt->mnt.mnt_flags = mnt_flags;
> 
> This can easily be compiled as:
> 
> mnt->mnt.mnt_flags &= ~MNT_USER_SETTABLE_MASK;
> mnt->mnt.mnt_flags |= mnt_flags;
> 
> (also 2 memory accesses, less register pressure)
> The flags are being concurrently read by e.g. do_mmap_pgoff()
> which does:
> 
> if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
> 
> As the result we can allow to mmap a MNT_NOEXEC mount
> as VM_EXEC.
> 
> Use WRITE_ONCE() to set new flags.
> 
> The data race was found with KernelThreadSanitizer (KTSAN).
> 
> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov

      reply	other threads:[~2015-09-21 14:06 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-21 12:16 Dmitry Vyukov
2015-09-21 14:06 ` Kirill A. Shutemov [this message]

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