From patchwork Fri Jun 17 10:25:59 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 891122 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p5HBIesa019766 for ; Fri, 17 Jun 2011 11:18:40 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756434Ab1FQK0P (ORCPT ); Fri, 17 Jun 2011 06:26:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60703 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755136Ab1FQK0O (ORCPT ); Fri, 17 Jun 2011 06:26:14 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id p5HAQ5ts029329 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 17 Jun 2011 06:26:05 -0400 Received: from warthog.procyon.org.uk ([10.3.112.12]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id p5HAQ035022911; Fri, 17 Jun 2011 06:26:02 -0400 Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 From: David Howells Subject: [PATCH] KEYS/DNS: Fix ____call_usermodehelper() to not lose the session keyring [ver #2] To: torvalds@osdl.org, akpm@linux-foundation.org Cc: jmorris@namei.org, shirishpargaonkar@gmail.com, keyrings@linux-nfs.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, David Howells , Eric Paris Date: Fri, 17 Jun 2011 11:25:59 +0100 Message-ID: <20110617102559.11413.50038.stgit@warthog.procyon.org.uk> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11 Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Fri, 17 Jun 2011 11:18:40 +0000 (UTC) ____call_usermodehelper() now erases any credentials set by the subprocess_inf::init() function. The problem is that: commit 17f60a7da150fdd0cfb9756f86a262daa72c835f Author: Eric Paris Date: Fri Apr 1 17:07:50 2011 -0400 capabilites: allow the application of capability limits to usermode helpers creates and commits new credentials with prepare_kernel_cred() after the call to the init() function. This wipes all keyrings after umh_keys_init() is called. The best way to deal with this is to put the init() call just prior to the commit_creds() call, and pass the cred pointer to init(). That means that umh_keys_init() and suchlike can modify the credentials _before_ they are published and potentially in use by the rest of the system. This prevents request_key() from working as it is prevented from passing the session keyring it set up with the authorisation token to /sbin/request-key, and so the latter can't assume the authority to instantiate the key. This causes the in-kernel DNS resolver to fail with ENOKEY unconditionally. Signed-off-by: David Howells Acked-by: Eric Paris Tested-by: Jeff Layton --- fs/exec.c | 2 +- include/linux/kmod.h | 8 ++++---- kernel/kmod.c | 16 +++++++++------- security/keys/request_key.c | 3 +-- 4 files changed, 15 insertions(+), 14 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/fs/exec.c b/fs/exec.c index 97e0d52..6075a1e 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1996,7 +1996,7 @@ static void wait_for_dump_helpers(struct file *file) * is a special value that we use to trap recursive * core dumps */ -static int umh_pipe_setup(struct subprocess_info *info) +static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) { struct file *rp, *wp; struct fdtable *fdt; diff --git a/include/linux/kmod.h b/include/linux/kmod.h index d4a5c84..0da38cf 100644 --- a/include/linux/kmod.h +++ b/include/linux/kmod.h @@ -45,7 +45,7 @@ static inline int request_module_nowait(const char *name, ...) { return -ENOSYS; #endif -struct key; +struct cred; struct file; enum umh_wait { @@ -62,7 +62,7 @@ struct subprocess_info { char **envp; enum umh_wait wait; int retval; - int (*init)(struct subprocess_info *info); + int (*init)(struct subprocess_info *info, struct cred *new); void (*cleanup)(struct subprocess_info *info); void *data; }; @@ -73,7 +73,7 @@ struct subprocess_info *call_usermodehelper_setup(char *path, char **argv, /* Set various pieces of state into the subprocess_info structure */ void call_usermodehelper_setfns(struct subprocess_info *info, - int (*init)(struct subprocess_info *info), + int (*init)(struct subprocess_info *info, struct cred *new), void (*cleanup)(struct subprocess_info *info), void *data); @@ -87,7 +87,7 @@ void call_usermodehelper_freeinfo(struct subprocess_info *info); static inline int call_usermodehelper_fns(char *path, char **argv, char **envp, enum umh_wait wait, - int (*init)(struct subprocess_info *info), + int (*init)(struct subprocess_info *info, struct cred *new), void (*cleanup)(struct subprocess_info *), void *data) { struct subprocess_info *info; diff --git a/kernel/kmod.c b/kernel/kmod.c index ad6a81c..47613df 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -156,12 +156,6 @@ static int ____call_usermodehelper(void *data) */ set_user_nice(current, 0); - if (sub_info->init) { - retval = sub_info->init(sub_info); - if (retval) - goto fail; - } - retval = -ENOMEM; new = prepare_kernel_cred(current); if (!new) @@ -173,6 +167,14 @@ static int ____call_usermodehelper(void *data) new->cap_inheritable); spin_unlock(&umh_sysctl_lock); + if (sub_info->init) { + retval = sub_info->init(sub_info, new); + if (retval) { + abort_creds(new); + goto fail; + } + } + commit_creds(new); retval = kernel_execve(sub_info->path, @@ -388,7 +390,7 @@ EXPORT_SYMBOL(call_usermodehelper_setup); * context in which call_usermodehelper_exec is called. */ void call_usermodehelper_setfns(struct subprocess_info *info, - int (*init)(struct subprocess_info *info), + int (*init)(struct subprocess_info *info, struct cred *new), void (*cleanup)(struct subprocess_info *info), void *data) { diff --git a/security/keys/request_key.c b/security/keys/request_key.c index d31862e..8e319a4 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -71,9 +71,8 @@ EXPORT_SYMBOL(complete_request_key); * This is called in context of freshly forked kthread before kernel_execve(), * so we can simply install the desired session_keyring at this point. */ -static int umh_keys_init(struct subprocess_info *info) +static int umh_keys_init(struct subprocess_info *info, struct cred *cred) { - struct cred *cred = (struct cred*)current_cred(); struct key *keyring = info->data; return install_session_keyring_to_cred(cred, keyring);