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[104.53.165.62]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-67934e2c25fsm17489d50.19.2026.10.08.11.41.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2026 11:41:57 -0700 (PDT) Date: Thu, 8 Oct 2026 13:41:55 -0500 From: Andrew Halaney To: Jarkko Sakkinen Cc: David Howells , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , Paul Moore , James Morris , "Serge E. Hallyn" , Eric Biggers , "Theodore Y. Ts'o" , Jonathan Corbet , Shuah Khan , Randy Dunlap , dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, bpf@vger.kernel.org, fsverity@lists.linux.dev, linux-doc@vger.kernel.org, "Christian Brauner (Amutable)" Subject: Re: [PATCH 1/3] keys: add KEY_SPEC_DM_VERITY_KEYRING Message-ID: References: <20260914-ajhalaney-dmverity-key-identifier-v1-0-01922dc1366a@amutable.com> <20260914-ajhalaney-dmverity-key-identifier-v1-1-01922dc1366a@amutable.com> <715249.1789718726@warthog.procyon.org.uk> Precedence: bulk X-Mailing-List: fsverity@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Oct 08, 2026 at 08:33:45PM +0300, Jarkko Sakkinen wrote: > On Wed, Oct 07, 2026 at 10:30:14AM -0500, Andrew Halaney wrote: > > On Fri, Sep 25, 2026 at 11:39:28AM +0300, Jarkko Sakkinen wrote: > > > On Fri, Sep 18, 2026 at 02:59:49PM -0500, Andrew Halaney wrote: > > > > On Fri, Sep 18, 2026 at 09:05:26AM +0100, David Howells wrote: > > > > > Jarkko Sakkinen wrote: > > > > > > > > > > > This is great for discussion but what we want for the commit message > > > > > > is just motivation and resolution. > > > > > > > > > > Actually, I think it's useful that Andrew wrote up the issues in the commit > > > > > message - and I think it shows part of the motivation. The 'writing a fake > > > > > /proc/keys line in the description' is something I hadn't considered. > > > > > > > > I'll defer to what you all want in the message here, I found it valuable > > > > but I trend on the side of overly verbose admittedly! > > > > > > > > > > > > > > > I don't think we need all this just to say that /proc/keys in a racy > > > > > > query mechanism for production, which is an issue for dm-verity, given > > > > > > that nothing else is available. > > > > > > > > > > I think at some point, we will need a system call to search all for all > > > > > accessible keys matching certain criteria by actually walking the key > > > > > database. The problem there is that there may be multiple hits, so we may > > > > > need something like: > > > > > > > > > > int count = find_key(key_serial_t start_id, > > > > > const char *type, const char *desc_prefix, > > > > > key_serial_t *results, size_t results_size, > > > > > unsigned int flags); > > > > > > > > > > Allowing you to do: > > > > > > > > > > key_serial_t dm_key; > > > > > int n = find_key(0, "keyring", ".dm_verity", &dm_key, 1, > > > > > FIND_KEY_EXACT_DESC); > > > > > > > > > > This wouldn't be as fast as a direct lookup since it would have to walk the > > > > > key tree, doing name comparisons and perm checks on each key of the type. > > > > > > > > > > > And secondly special keys are meant for implicit keyrings so isn't > > > > > > that all there's to it? > > > > > > > > > > I have no particular objection to setting aside a block of negative key IDs > > > > > for special keyrings that need to be accessed a lot - though I would make > > > > > common reg/unreg functions that take the ID to be registered and, say, set the > > > > > block at -257..-512. Moving the BFP keyring to -257 and DM to -258. > > > > > > > > To be clear are you suggesting I do that for v2 here? Happy to make the > > > > change and add some reuse to the registration functions, etc. I'm > > > > guessing its fine to change the bpf id since its still only in -next? > > > > > > > > The only awkward bit with making that more generic is that dm-verity > > > > isn't __ro_after_init since its coming from a module possibly, and > > > > because of the module usage I also protected it with a spinlock in case > > > > someone's accessing it while you unload the module. Could just use one > > > > spinlock for the whole generic array, and drop the __ro_after_init I > > > > suppose. > > > > > > > > Let me know if I'm not following properly! > > > > > > I just read David's response and I think he made fair arguments, > > > and patches look fine to me. > > > > > > David, did you have anything? I could pick these. > > > > > > Reviewed-by: Jarkko Sakkinen > > > > > > > Gentle ping :) > > Understandable :-) > > > > > Are we happy with these to get picked up? > > Can you just do a resend that applies on top of latest mainline > or my tree? I.e. b4 shazam was not happy about this. > > Full log: > > $ b4 shazam https://lore.kernel.org/keyrings/20260914-ajhalaney-dmverity-key-identifier-v1-2-01922dc1366a@amutable.com/ > Grabbing thread from lore.kernel.org/all/20260914-ajhalaney-dmverity-key-identifier-v1-2-01922dc1366a@amutable.com/t.mbox.gz > > Breaking thread to remove parents of 20260914-ajhalaney-dmverity-key-identifier-v1-0-01922dc1366a@amutable.com > Checking for newer revisions > Grabbing search results from lore.kernel.org > Analyzing 10 messages in the thread > Analyzing 0 code-review messages > Checking attestation on all messages, may take a moment... > --- > ✗ [PATCH 1/3] keys: add KEY_SPEC_DM_VERITY_KEYRING > + Reviewed-by: Jarkko Sakkinen (✓ DKIM/kernel.org) > + Reviewed-by: Christian Brauner (Amutable) (✓ DKIM/kernel.org) > ✗ [PATCH 2/3] keys: add KEY_SPEC_FS_VERITY_KEYRING > + Reviewed-by: Christian Brauner (Amutable) (✓ DKIM/kernel.org) > ✗ [PATCH 3/3] Documentation: keys: document IDs added since KEY_SPEC_REQKEY_AUTH_KEY > + Reviewed-by: Christian Brauner (Amutable) (✓ DKIM/kernel.org) > --- > ✗ BADSIG: DKIM/amutable-com.20251104.gappssmtp.com > --- > Total patches: 3 > --- > Base: base-commit 1a1de54f7369cd2b5bac0f265910e60ad3a6b4c3 not known, ignoring > Applying: keys: add KEY_SPEC_DM_VERITY_KEYRING > Patch failed at 0001 keys: add KEY_SPEC_DM_VERITY_KEYRING > error: patch failed: include/linux/key.h:441 > error: include/linux/key.h: patch does not apply > error: patch failed: include/uapi/linux/keyctl.h:25 > error: include/uapi/linux/keyctl.h: patch does not apply > error: patch failed: security/keys/process_keys.c:25 > error: security/keys/process_keys.c: patch does not apply > hint: Use 'git am --show-current-patch=diff' to see the failed patch > hint: When you have resolved this problem, run "git am --continue". > hint: If you prefer to skip this patch, run "git am --skip" instead. > hint: To restore the original branch and stop patching, run "git am --abort". > hint: Disable this message with "git config advice.mergeConflict false" Egh, sorry I was on linux-next. I'm also realizing that the KEY_SPEC_BPF_KEYRING bit this sort of depends on is only in bpf-next (i.e. 264d8fd2794f ("bpf, keys: Add a bpf keyring for program signature validation")). Otherwise as is this conflicts on mainline and we'd just have to skip the -9 the bpf keyring is using at the moment. Should I just base on bpf-next that and send thru there instead? I can't recall how kernel maintainers typically handle this other than cutting a stable branch that both subsystems pull from, etc. Thanks, Andrew