From mboxrd@z Thu Jan 1 00:00:00 1970 From: hch@infradead.org (Christoph Hellwig) Date: Sun, 17 Sep 2017 08:37:55 -0700 Subject: [PATCH 3/3] ima: use fs method to read integrity data (updated patch description) In-Reply-To: References: <1505451494-30228-1-git-send-email-zohar@linux.vnet.ibm.com> <1505451494-30228-4-git-send-email-zohar@linux.vnet.ibm.com> <1505507142.4200.103.camel@linux.vnet.ibm.com> <20170917151757.GA14262@infradead.org> Message-ID: <20170917153755.GA21193@infradead.org> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org On Sun, Sep 17, 2017 at 08:28:40AM -0700, Linus Torvalds wrote: > The issue is that somebody else can come in - using direct IO - at the > same time as the first person is collecting measurements, and thus > race with the collector. > > So now the measurements are not trustworthy any more. Yes. And it's always been that way with IMA. > .. and *my* point is that it's the wrong lock for actually checking > integrity (it doesn't actually guarantee exclusion, even though in > practice it's almost always the case), and so we're adding a nasty > callback that in 99% of all cases is the same as the normal read, and > we *could* have just added it with a RWF flag instead. > > Is there some reason why integrity has to use that particular lock > that is so inconvenient for the filesystems it wants to check? I'll have to defer that to Mimi - I just jumped into this whole mess to help fixing the deadlocks we saw on XFS and NFS. Unfortunately the whole security code is a giant mess that doesn't document assumptions, threat models or gets any sort of verification of those through automated testing. -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html