linux-kernel - [PATCH] Subject: [PATCH] KEYS: Handle there being no fallback destination keyring for request

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20090409161405.5329.86573.stgit@warthog.procyon.org.uk>
Date:	Thu, 09 Apr 2009 17:14:05 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	dhowells@...hat.com, jlayton@...hat.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH] Subject: [PATCH] KEYS: Handle there being no fallback
	destination keyring for request_key()

When request_key() is called, without there being any standard process
keyrings on which to fall back if a destination keyring is not specified, an
oops is liable to occur when construct_alloc_key() calls down_write() on
dest_keyring's semaphore.

Due to function inlining this may be seen as an oops in down_write() as called
from request_key_and_link().

This situation crops up during boot, where request_key() is called from within
the kernel (such as in CIFS mounts) where nobody is actually logged in, and so
PAM has not had a chance to create a session keyring and user keyrings to act
as the fallback.

To fix this, make construct_alloc_key() not attempt to cache a key if there is
no fallback key if no destination keyring is given specifically.

Signed-off-by: David Howells <dhowells@...hat.com>
Tested-by: Jeff Layton <jlayton@...hat.com>
---

 security/keys/request_key.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)


diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 22a3158..03fe63e 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -311,7 +311,8 @@ static int construct_alloc_key(struct key_type *type,
 
 	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
 
-	down_write(&dest_keyring->sem);
+	if (dest_keyring)
+		down_write(&dest_keyring->sem);
 
 	/* attach the key to the destination keyring under lock, but we do need
 	 * to do another check just in case someone beat us to it whilst we
@@ -322,10 +323,12 @@ static int construct_alloc_key(struct key_type *type,
 	if (!IS_ERR(key_ref))
 		goto key_already_present;
 
-	__key_link(dest_keyring, key);
+	if (dest_keyring)
+		__key_link(dest_keyring, key);
 
 	mutex_unlock(&key_construction_mutex);
-	up_write(&dest_keyring->sem);
+	if (dest_keyring)
+		up_write(&dest_keyring->sem);
 	mutex_unlock(&user->cons_lock);
 	*_key = key;
 	kleave(" = 0 [%d]", key_serial(key));

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/