From patchwork Mon Feb 3 10:28:08 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Brodsky X-Patchwork-Id: 13957269 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 76B31C02192 for ; Mon, 3 Feb 2025 10:56:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=VjrjF09VQnxDeNYh4e1Ha75V6UufRCaFP71EexFz7fY=; b=KqtbKC4JcNQY+dH0QQ0cFOEyQq ibI+cn4HhXYRzN/Wb9XqcXpaoBH4cpcwITaTt0D8EG/RIusnGAKRdp0O1Akx1+ZpUQsPdN7Fxw4qU keRPABoAgwzFaUr57voG5lT3mndHdbaDSNVoMDrDlZYu6S0XRwLtpdxZ3/3vQe3wHMZRj4HcslvZE D3ZQbme/5di/DtJ27xVA132pGCilJ8AN6xhf65qPrTZvA2fafFiyqld/T0UHqvhhhWlpUu8twxkug BHUqFUkfDau1CCjzFPaHifIF01eMCFk+SPtcm4U+t+s/8hnNTKieHx8FQ+XYjFMR6OivPkzrU/9of 548orzVA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1teu7V-0000000FAbk-1JSJ; Mon, 03 Feb 2025 10:56:01 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tethI-0000000F7Ts-11KZ for linux-arm-kernel@lists.infradead.org; Mon, 03 Feb 2025 10:28:58 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 480031BC0; Mon, 3 Feb 2025 02:29:20 -0800 (PST) Received: from e123572-lin.arm.com (e123572-lin.cambridge.arm.com [10.1.194.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 196943F63F; Mon, 3 Feb 2025 02:28:51 -0800 (PST) From: Kevin Brodsky To: linux-hardening@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , Andrew Morton , Mark Brown , Catalin Marinas , Dave Hansen , David Howells , "Eric W. Biederman" , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Andy Lutomirski , Marc Zyngier , Peter Zijlstra , Pierre Langlois , Quentin Perret , "Mike Rapoport (IBM)" , Ryan Roberts , Thomas Gleixner , Will Deacon , Matthew Wilcox , Qi Zheng , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org Subject: [RFC PATCH 7/8] fs: Protect creds installed by override_creds() Date: Mon, 3 Feb 2025 10:28:08 +0000 Message-ID: <20250203102809.1223255-8-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250203102809.1223255-1-kevin.brodsky@arm.com> References: <20250203102809.1223255-1-kevin.brodsky@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250203_022856_368952_519639DC X-CRM114-Status: GOOD ( 18.59 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The kpkeys_hardened_cred feature, when enabled, automatically protects credentials installed by commit_creds(). However, because override_creds() does not consume its argument, it is up to its callers to protect the credentials before calling override_creds(). This is done by calling protect_creds(), moving the credentials to a protected memory location. In some cases, the credentials returned by prepare_creds() are passed to override_creds() as-is. In such situation where write access to the credentials is not needed, prepare_protected_creds() is used to avoid the copy incurred by a separate call to protect_creds(). This patch covers the main users of override_creds(), but it is not comprehensive. This patch is a no-op if kpkeys_hardened_cred isn't enabled. Signed-off-by: Kevin Brodsky --- fs/aio.c | 2 +- fs/fuse/passthrough.c | 2 +- fs/nfs/nfs4idmap.c | 2 +- fs/nfsd/auth.c | 2 +- fs/nfsd/nfs4recover.c | 2 +- fs/nfsd/nfsfh.c | 2 +- fs/open.c | 2 +- fs/overlayfs/dir.c | 2 +- fs/overlayfs/super.c | 2 +- 9 files changed, 9 insertions(+), 9 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 7b976b564cfc..ab9f4c8d778a 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1657,7 +1657,7 @@ static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb, if (unlikely(!req->file->f_op->fsync)) return -EINVAL; - req->creds = prepare_creds(); + req->creds = prepare_protected_creds(); if (!req->creds) return -ENOMEM; diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c index 607ef735ad4a..4451651b1e51 100644 --- a/fs/fuse/passthrough.c +++ b/fs/fuse/passthrough.c @@ -248,7 +248,7 @@ int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map) goto out_fput; fb->file = file; - fb->cred = prepare_creds(); + fb->cred = prepare_protected_creds(); refcount_set(&fb->count, 1); res = fuse_backing_id_alloc(fc, fb); diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c index 25a7c771cfd8..6ff25dd5c2fb 100644 --- a/fs/nfs/nfs4idmap.c +++ b/fs/nfs/nfs4idmap.c @@ -228,7 +228,7 @@ int nfs_idmap_init(void) set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags); cred->thread_keyring = keyring; cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; - id_resolver_cache = cred; + id_resolver_cache = protect_creds(cred); return 0; failed_reg_legacy: diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c index 4dc327e02456..09b377a97147 100644 --- a/fs/nfsd/auth.c +++ b/fs/nfsd/auth.c @@ -79,7 +79,7 @@ int nfsd_setuser(struct svc_cred *cred, struct svc_export *exp) else new->cap_effective = cap_raise_nfsd_set(new->cap_effective, new->cap_permitted); - put_cred(override_creds(new)); + put_cred(override_creds(protect_creds(new))); return 0; oom: diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c index 28f4d5311c40..095664648103 100644 --- a/fs/nfsd/nfs4recover.c +++ b/fs/nfsd/nfs4recover.c @@ -81,7 +81,7 @@ nfs4_save_creds(const struct cred **original_creds) new->fsuid = GLOBAL_ROOT_UID; new->fsgid = GLOBAL_ROOT_GID; - *original_creds = override_creds(new); + *original_creds = override_creds(protect_creds(new)); return 0; } diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c index 32019751a41e..d64d23e9357e 100644 --- a/fs/nfsd/nfsfh.c +++ b/fs/nfsd/nfsfh.c @@ -221,7 +221,7 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net, new->cap_effective = cap_raise_nfsd_set(new->cap_effective, new->cap_permitted); - put_cred(override_creds(new)); + put_cred(override_creds(protect_creds(new))); } else { error = nfsd_setuser_and_check_port(rqstp, cred, exp); if (error) diff --git a/fs/open.c b/fs/open.c index 932e5a6de63b..3b5331b7c0f0 100644 --- a/fs/open.c +++ b/fs/open.c @@ -457,7 +457,7 @@ static const struct cred *access_override_creds(void) * freeing. */ override_cred->non_rcu = 1; - return override_creds(override_cred); + return override_creds(protect_creds(override_cred)); } static long do_faccessat(int dfd, const char __user *filename, int mode, int flags) diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index c9993ff66fc2..943ec4300ddb 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -580,7 +580,7 @@ static const struct cred *ovl_setup_cred_for_create(struct dentry *dentry, * We must be called with creator creds already, otherwise we risk * leaking creds. */ - old_cred = override_creds(override_cred); + old_cred = override_creds(protect_creds(override_cred)); WARN_ON_ONCE(old_cred != ovl_creds(dentry->d_sb)); return override_cred; diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 86ae6f6da36b..3489a62c5d8a 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1318,7 +1318,7 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc) sb->s_d_op = &ovl_dentry_operations; err = -ENOMEM; - ofs->creator_cred = cred = prepare_creds(); + ofs->creator_cred = cred = prepare_protected_creds(); if (!cred) goto out_err;