From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yx1-f48.google.com (mail-yx1-f48.google.com [74.125.224.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B55966FC5 for ; Mon, 14 Sep 2026 16:42:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.224.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789404126; cv=none; b=Dd6hFc03k5BLeiy5d5uc8zG/LAdSOhIDgMC6fdeT5n8RP8Qx97K8Li0P10s9rV9tu8CJPy2lTcgXMwZ4I0Psm8S15ZBsJkKFXGKXMty5zvTxLhCsl3UOiKGwcwtqdcdj5MzOE2s6hlGm1FIRbvl8e2ojnfDcPlDKuMDxL08Wk4w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789404126; c=relaxed/simple; bh=+N9ZKaZxeybEwISedHcLFR5weaHCuqwm361zoPMxU4M=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=CLeS1ghuFCLr5/U4xlvav5a8Jy9YcGe1h52pN4+R8f5BDlCLyYhZXkIwYqULG9aTZA1DQBo7zGy5ugsZ2tasC8y3EFV7kXpPU4LQOGJLY11buvSrDboaEIMt+nLMtiZTj76km56D80l3bYd1dgD4wj9calB0iQN8z1nl2WAgso0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=amutable.com; spf=pass smtp.mailfrom=amutable.com; dkim=pass (2048-bit key) header.d=amutable-com.20251104.gappssmtp.com header.i=@amutable-com.20251104.gappssmtp.com header.b=WO9bU0iX; arc=none smtp.client-ip=74.125.224.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=amutable.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amutable.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amutable-com.20251104.gappssmtp.com header.i=@amutable-com.20251104.gappssmtp.com header.b="WO9bU0iX" Received: by mail-yx1-f48.google.com with SMTP id 956f58d0204a3-66bd7857841so3346631d50.3 for ; Mon, 14 Sep 2026 09:42:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amutable-com.20251104.gappssmtp.com; s=20251104; t=1789404122; x=1790008922; darn=vger.kernel.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :content-type:mime-version:subject:date:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=SfEDwKZx2Ac2Zov3iFEW2DHPNztOR7nlXE153PDtqAw=; b=WO9bU0iXJcOVnCevtYrA5YksA5xFDXQ33CN3bwdR5wFYR3c398KJiptiBuY0ULyzCZ VcErnYSK+FGhwrruzXoMb0SG9cgAyv/JZ+AmjramI9rYv34AzMHMrnuv0O68jz9Lyh2C e1bFg3Nb90skmXYQx4dX4+/t/ztlH7j17ezNUkxeudEi8jDYQtyt2dCGTMKRB5XXZnCS ACByqlzdtrGsqbKRKHfpsegxqgyiBWyLNJFnijxj+BVjbMjeUlr9+Az/eGYT8nmKYeEw vzQFjZSxzdnugfHpf3NRdR2TWpLDE7hf1OgpeJu9rqYc+HG9JqXYqvsLYmB00TC2Rmpq EICQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1789404122; x=1790008922; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :content-type:mime-version:subject:date:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=SfEDwKZx2Ac2Zov3iFEW2DHPNztOR7nlXE153PDtqAw=; b=cONd7a0X4etanjqt0odSi7F0cIUxsv9cFIwEvFZugEWq2Ba6lv2RlQECaCvSAeoagL uFNC/oEnlAYw77v/uGI8i/jvzCupX5XeefExW4ZxF+fn2NMaQ8aXqmwUB/hQktQvS+N5 mEfdpWSz2XJFzKEJ5tI+sSgqKvcTELg4JYMv5MQdjey1I/s3X3yFGLw8F4glKY/GMZYD ZX/QxzLRU/gPyjVKnzTjC6uak2s8BsROniq983spJ0EgW/myoAjgfA/B11OcXHakL6sp CdILhyo+5/2GLSfTNGLRGbfkbMCKvDm2Eq+NDgJXUqpP70y94LqJ6yaVJXqsMtdPc7+y Bs9A== X-Forwarded-Encrypted: i=1; AKwUvBya2NgIipmIR70V3SaoJpG3jltzQlp+8ZXD8xOwm93gA9qjvnV0lNIJe5OpBa8Gya6Mr3UqiTsq8/k=@vger.kernel.org X-Gm-Message-State: AFuF++l1pVywewo2KCXtiIeN9MAe/sd4C4vJE51j/N6FfOTth1clAaBT 7zSf7hzz9f40AtxVdiyVin57GsNxSSSnesD9wFnwM28eLltlFc4rdiIiTW32aNcvoD2a X-Gm-Gg: AYBFou1mljAQ9xXCVQvemefGMOQj8dlW8no0di+32EK2n7uWdwI9r24X94GH8MurvIO ZSUHo7ei60RICAtXWB7TcdwqDO0X4pnXbsBADzYOHl1wpKKlB/69ZLZwYEwg7Y/JCqOC/NfEV/S 9UQUAxftkSaT/HUogu9AxFRo+SHMxcN6ROS3CLMVhOvaL1W1X+EXEUMENIgbrLsR+giWE7IuSp3 sxJUiFZ58fwlezKLArdh4lG0jI2c7i7c3x6mi7eiO6qo0vy/quWPix6nPDSDRjjKQszleZlMM8V b0flzfyA2yFu//CbsXSY3ZEiz8IVBl1zYaiGkMzHxmlp++MtIuDKhxiCEiGPtY0OPm/AiDVTfPt 4cK303OSkslTOv3pdTUDXZi9asjWTrHCTRmCVnBfvt6iMmVlD9xqwipK59oftQ3JV4+uu596a3Z JiGHYshZyukQ8Vx3pQBZCu4PcMhW+mkiMfB/0DFo+lppHy0hQu+JTmaTgjwreBPQ== X-Received: by 2002:a53:ac83:0:b0:66f:c1bc:c097 with SMTP id 956f58d0204a3-6714e1a194cmr1022205d50.95.1789404121718; Mon, 14 Sep 2026 09:42:01 -0700 (PDT) Received: from [192.168.1.110] ([2600:1700:1ff0:d0ef::d15]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-67125df42a8sm4879023d50.8.2026.09.14.09.42.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 09:42:01 -0700 (PDT) From: Andrew Halaney Date: Mon, 14 Sep 2026 11:41:42 -0500 Subject: [PATCH 1/3] keys: add KEY_SPEC_DM_VERITY_KEYRING Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260914-ajhalaney-dmverity-key-identifier-v1-1-01922dc1366a@amutable.com> References: <20260914-ajhalaney-dmverity-key-identifier-v1-0-01922dc1366a@amutable.com> In-Reply-To: <20260914-ajhalaney-dmverity-key-identifier-v1-0-01922dc1366a@amutable.com> To: Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , David Howells , Jarkko Sakkinen , Paul Moore , James Morris , "Serge E. Hallyn" , Eric Biggers , "Theodore Y. Ts'o" , Jonathan Corbet , Shuah Khan , Randy Dunlap Cc: 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, Andrew Halaney , "Christian Brauner (Amutable)" X-Mailer: b4 0.14.3 The .dm-verity keyring is not linked into any process keyring, so request_key() and KEYCTL_SEARCH cannot find it. Userspace has to scrape /proc/keys for the serial to use. That's not great, one could put in a bogus description containing a newline to confuse userspace further. For example, thanks to AI models, which I run as root but you could show off as any old user: # DESC=$'.dm-verity: 1\n0badf00d I--Q--- 1 perm 082f0000 0 0 keyring .dm-verity' # k=$(echo -n "1234567" | keyctl padd user "$DESC" @s) # keyctl setperm "$k" 0x3f010001 # cat /proc/keys | grep dm-verity 10402023 I------ 2 perm 082f0000 0 0 keyring .dm-verity: empty 12e0bee6 I--Q--- 1 perm 3f010001 0 0 user .dm-verity: 1 0badf00d I--Q--- 1 perm 082f0000 0 0 keyring .dm-verity: 7 0x0badf00d is not a keyring, it is the text inside our user's key description. Telling the two apart needs a KEYCTL_DESCRIBE per row which is annoying to do. i.e.: # keyctl rdescribe 0x10402023 keyring;0;0;082f0000;.dm-verity # keyctl rdescribe 0x0badf00d keyctl_describe: Required key not available Let's just give it a well known identifier, i.e.: # keyctl rdescribe -10 keyring;0;0;082f0000;.dm-verity This is exactly what commit 264d8fd2794f ("bpf, keys: Add a bpf keyring for program signature validation") did, and was the inspiration for this commit minus the spinlock bits required due to dm-verity being a module. Suggested-by: Christian Brauner (Amutable) Signed-off-by: Andrew Halaney --- drivers/md/dm-verity-verify-sig.c | 3 +++ include/linux/key.h | 1 + include/uapi/linux/keyctl.h | 1 + security/keys/process_keys.c | 33 +++++++++++++++++++++++++++++++++ 4 files changed, 38 insertions(+) diff --git a/drivers/md/dm-verity-verify-sig.c b/drivers/md/dm-verity-verify-sig.c index b2b55c41e2cb..da509dcdd7e5 100644 --- a/drivers/md/dm-verity-verify-sig.c +++ b/drivers/md/dm-verity-verify-sig.c @@ -189,11 +189,14 @@ int __init dm_verity_verify_sig_init(void) keyring_restrict(make_key_ref(dm_verity_keyring, true), NULL, NULL)) panic("dm-verity can't seal keyring\n"); + key_register_dm_verity_keyring(dm_verity_keyring); + return 0; } void dm_verity_verify_sig_exit(void) { + key_register_dm_verity_keyring(NULL); key_revoke(dm_verity_keyring); key_put(dm_verity_keyring); } diff --git a/include/linux/key.h b/include/linux/key.h index bd10fe45819d..ae8d3314fd93 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -441,6 +441,7 @@ extern int keyring_restrict(key_ref_t keyring, const char *type, const char *restriction); extern void key_register_bpf_keyring(struct key *keyring); +extern void key_register_dm_verity_keyring(struct key *keyring); extern struct key *key_lookup(key_serial_t id); diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h index fa85b9760391..75923941f1b3 100644 --- a/include/uapi/linux/keyctl.h +++ b/include/uapi/linux/keyctl.h @@ -25,6 +25,7 @@ #define KEY_SPEC_REQKEY_AUTH_KEY -7 /* - key ID for assumed request_key auth key */ #define KEY_SPEC_REQUESTOR_KEYRING -8 /* - key ID for request_key() dest keyring */ #define KEY_SPEC_BPF_KEYRING -9 /* - key ID for the BPF-specific keyring */ +#define KEY_SPEC_DM_VERITY_KEYRING -10 /* - key ID for the .dm-verity keyring */ /* request-key default keyrings */ #define KEY_REQKEY_DEFL_NO_CHANGE -1 diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index 44358388e395..dba3df41638b 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -25,6 +25,10 @@ static DEFINE_MUTEX(key_session_mutex); /* BPF keyring reachable through KEY_SPEC_BPF_KEYRING */ static struct key *bpf_keyring __ro_after_init; +/* dm-verity keyring reachable through KEY_SPEC_DM_VERITY_KEYRING */ +static struct key *dm_verity_keyring; +static DEFINE_SPINLOCK(dm_verity_keyring_lock); + /* The root user's tracking struct */ struct key_user root_key_user = { .usage = REFCOUNT_INIT(3), @@ -607,6 +611,24 @@ void key_register_bpf_keyring(struct key *keyring) bpf_keyring = keyring; } +/** + * key_register_dm_verity_keyring - Publish the keyring for KEY_SPEC_DM_VERITY_KEYRING + * @keyring: The keyring to publish, or NULL to withdraw it + * + * Make @keyring reachable by userspace through the KEY_SPEC_DM_VERITY_KEYRING + * special key ID, so that provisioning it does not require scraping its + * serial out of /proc/keys first. dm-verity can be unloaded as a module + * and the keyring deregistered, as such serialize access with + * dm_verity_keyring_lock. + */ +void key_register_dm_verity_keyring(struct key *keyring) +{ + spin_lock(&dm_verity_keyring_lock); + dm_verity_keyring = keyring; + spin_unlock(&dm_verity_keyring_lock); +} +EXPORT_SYMBOL_GPL(key_register_dm_verity_keyring); + /* * Look up a key ID given us by userspace with a given permissions mask to get * the key it refers to. @@ -766,6 +788,17 @@ key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags, key_ref = make_key_ref(key, 0); break; + case KEY_SPEC_DM_VERITY_KEYRING: + spin_lock(&dm_verity_keyring_lock); + key = dm_verity_keyring; + if (key) + __key_get(key); + spin_unlock(&dm_verity_keyring_lock); + if (!key) + goto error; + key_ref = make_key_ref(key, 0); + break; + default: key_ref = ERR_PTR(-EINVAL); if (id < 1) -- 2.55.0