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authorDavid Howells <dhowells@redhat.com>2010-07-22 12:53:18 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2010-07-22 09:42:40 -0700
commit4c0c03ca54f72fdd5912516ad0a23ec5cf01bda7 (patch)
treea05cfa65c298edb1f034923ff6eb76839b5bc0dd /include
parentcd5b8f8755a89a57fc8c408d284b8b613f090345 (diff)
downloadlinux-2.6.34-ux500-4c0c03ca54f72fdd5912516ad0a23ec5cf01bda7.tar.gz
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 <dhowells@redhat.com> Reviewed-and-Tested-by: Jeff Layton <jlayton@redhat.com> Acked-by: Steve French <smfrench@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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