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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 16 Nov 2020 10:09:28 -0800
Message-ID: <CAHk-=wjd0RNthZQTLVsnK_d9SFYH0rug2tkezLLB0J-YZzVC+Q@mail.gmail.com>
Subject: Re: [RESEND][PATCH] ima: Set and clear FMODE_CAN_READ in ima_calc_file_hash()
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Mimi Zohar <zohar@linux.ibm.com>,
        Roberto Sassu <roberto.sassu@huawei.com>,
        "linux-integrity@vger.kernel.org" <linux-integrity@vger.kernel.org>,
        "linux-security-module@vger.kernel.org" 
        <linux-security-module@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Silviu Vlasceanu <Silviu.Vlasceanu@huawei.com>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
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On Mon, Nov 16, 2020 at 9:41 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> The "issue" with IMA is that it uses security hooks to hook into the
> VFS and then wants to read every file that gets opened on a real file
> system to "measure" the contents vs a hash stashed away somewhere.

Well, but that's easy enough to handle: if the open isn't a read open,
then the old contents don't matter, so you shouldn't bother to measure
the file.

So this literally sounds like a "doctor, doctor, it hurts when I hit
my head with a hammer" situation..

         Linus