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Date:   Thu, 17 Oct 2019 04:15:46 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     linux-fsdevel@vger.kernel.org,
        Deepa Dinamani <deepa.kernel@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>, Jeff Layton <jlayton@kernel.org>
Subject: Re: [PATCH v2] fs/namespace.c: fix use-after-free of mount in
 mnt_warn_timestamp_expiry()
Message-ID: <20191017031546.GT26530@ZenIV.linux.org.uk>
References: <20191017024814.61980-1-ebiggers@kernel.org>
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On Wed, Oct 16, 2019 at 07:48:14PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> After do_add_mount() returns success, the caller doesn't hold a
> reference to the 'struct mount' anymore.  So it's invalid to access it
> in mnt_warn_timestamp_expiry().
> 
> Fix it by calling mnt_warn_timestamp_expiry() before do_add_mount()
> rather than after, and adjusting the warning message accordingly.
> 
> Reported-by: syzbot+da4f525235510683d855@syzkaller.appspotmail.com
> Fixes: f8b92ba67c5d ("mount: Add mount warning for impending timestamp expiry")
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Applied to #fixes and pushed