From 4c0c03ca54f72fdd5912516ad0a23ec5cf01bda7 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 22 Jul 2010 12:53:18 +0100 Subject: CIFS: Fix a malicious redirect problem in the DNS lookup code Fix the security problem in the CIFS filesystem DNS lookup code in which a malicious redirect could be installed by a random user by simply adding a result record into one of their keyrings with add_key() and then invoking a CIFS CFS lookup [CVE-2010-2524]. This is done by creating an internal keyring specifically for the caching of DNS lookups. To enforce the use of this keyring, the module init routine creates a set of override credentials with the keyring installed as the thread keyring and instructs request_key() to only install lookup result keys in that keyring. The override is then applied around the call to request_key(). This has some additional benefits when a kernel service uses this module to request a key: (1) The result keys are owned by root, not the user that caused the lookup. (2) The result keys don't pop up in the user's keyrings. (3) The result keys don't come out of the quota of the user that caused the lookup. The keyring can be viewed as root by doing cat /proc/keys: 2a0ca6c3 I----- 1 perm 1f030000 0 0 keyring .dns_resolver: 1/4 It can then be listed with 'keyctl list' by root. # keyctl list 0x2a0ca6c3 1 key in keyring: 726766307: --alswrv 0 0 dns_resolver: foo.bar.com Signed-off-by: David Howells Reviewed-and-Tested-by: Jeff Layton Acked-by: Steve French Signed-off-by: Linus Torvalds --- fs/cifs/cifsfs.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs/cifs/cifsfs.c') diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c index 484e52bb40bb..2cb1a70214d7 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -923,7 +923,7 @@ init_cifs(void) goto out_unregister_filesystem; #endif #ifdef CONFIG_CIFS_DFS_UPCALL - rc = register_key_type(&key_type_dns_resolver); + rc = cifs_init_dns_resolver(); if (rc) goto out_unregister_key_type; #endif @@ -935,7 +935,7 @@ init_cifs(void) out_unregister_resolver_key: #ifdef CONFIG_CIFS_DFS_UPCALL - unregister_key_type(&key_type_dns_resolver); + cifs_exit_dns_resolver(); out_unregister_key_type: #endif #ifdef CONFIG_CIFS_UPCALL @@ -961,7 +961,7 @@ exit_cifs(void) cifs_proc_clean(); #ifdef CONFIG_CIFS_DFS_UPCALL cifs_dfs_release_automount_timer(); - unregister_key_type(&key_type_dns_resolver); + cifs_exit_dns_resolver(); #endif #ifdef CONFIG_CIFS_UPCALL unregister_key_type(&cifs_spnego_key_type); -- cgit v1.2.3