Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932089AbaFWP3F (ORCPT ); Mon, 23 Jun 2014 11:29:05 -0400 Received: from g4t3427.houston.hp.com ([15.201.208.55]:36097 "EHLO g4t3427.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754091AbaFWP3C (ORCPT ); Mon, 23 Jun 2014 11:29:02 -0400 From: Waiman Long To: Paul Moore , Stephen Smalley , Eric Paris , James Morris Cc: linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Scott J Norton , Waiman Long Subject: [PATCH v3] selinux: no recursive read_lock of policy_rwlock in security_genfs_sid() Date: Mon, 23 Jun 2014 11:28:51 -0400 Message-Id: <1403537331-38759-1-git-send-email-Waiman.Long@hp.com> X-Mailer: git-send-email 1.7.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With the introduction of fair queued rwlock, recursive read_lock() may hang the offending process if there is a write_lock() somewhere in between. With recursive read_lock checking enabled, the following error was reported: ============================================= [ INFO: possible recursive locking detected ] 3.16.0-rc1 #2 Tainted: G E --------------------------------------------- load_policy/708 is trying to acquire lock: (policy_rwlock){.+.+..}, at: [] security_genfs_sid+0x3a/0x170 but task is already holding lock: (policy_rwlock){.+.+..}, at: [] security_fs_use+0x2c/0x110 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(policy_rwlock); lock(policy_rwlock); This patch fixes the occurrence of recursive read_lock() of policy_rwlock by adding a helper function __security_genfs_sid() which requires caller to take the lock before calling it. The security_fs_use() was then modified to call the new helper function. Signed-off-by: Waiman Long --- security/selinux/ss/services.c | 41 +++++++++++++++++++++++++++++++-------- 1 files changed, 32 insertions(+), 9 deletions(-) diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c index 4bca494..2aa9d17 100644 --- a/security/selinux/ss/services.c +++ b/security/selinux/ss/services.c @@ -2277,7 +2277,7 @@ out: } /** - * security_genfs_sid - Obtain a SID for a file in a filesystem + * __security_genfs_sid - Helper to obtain a SID for a file in a filesystem * @fstype: filesystem type * @path: path from root of mount * @sclass: file security class @@ -2286,11 +2286,13 @@ out: * Obtain a SID to use for a file in a filesystem that * cannot support xattr or use a fixed labeling behavior like * transition SIDs or task SIDs. + * + * The caller must acquire the policy_rwlock before calling this function. */ -int security_genfs_sid(const char *fstype, - char *path, - u16 orig_sclass, - u32 *sid) +static inline int __security_genfs_sid(const char *fstype, + char *path, + u16 orig_sclass, + u32 *sid) { int len; u16 sclass; @@ -2301,8 +2303,6 @@ int security_genfs_sid(const char *fstype, while (path[0] == '/' && path[1] == '/') path++; - read_lock(&policy_rwlock); - sclass = unmap_class(orig_sclass); *sid = SECINITSID_UNLABELED; @@ -2336,11 +2336,33 @@ int security_genfs_sid(const char *fstype, *sid = c->sid[0]; rc = 0; out: - read_unlock(&policy_rwlock); return rc; } /** + * security_genfs_sid - Obtain a SID for a file in a filesystem + * @fstype: filesystem type + * @path: path from root of mount + * @sclass: file security class + * @sid: SID for path + * + * Acquire policy_rwlock before calling __security_genfs_sid() and release + * it afterward. + */ +int security_genfs_sid(const char *fstype, + char *path, + u16 orig_sclass, + u32 *sid) +{ + int retval; + + read_lock(&policy_rwlock); + retval = __security_genfs_sid(fstype, path, orig_sclass, sid); + read_unlock(&policy_rwlock); + return retval; +} + +/** * security_fs_use - Determine how to handle labeling for a filesystem. * @sb: superblock in question */ @@ -2370,7 +2392,8 @@ int security_fs_use(struct super_block *sb) } sbsec->sid = c->sid[0]; } else { - rc = security_genfs_sid(fstype, "/", SECCLASS_DIR, &sbsec->sid); + rc = __security_genfs_sid(fstype, "/", SECCLASS_DIR, + &sbsec->sid); if (rc) { sbsec->behavior = SECURITY_FS_USE_NONE; rc = 0; -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/