This fixes CVE-2014-0102. The following command sequence produces an oops: keyctl new_session i=`keyctl newring _ses @s` keyctl link @s $i The problem is that search_nested_keyrings() sees two keyrings that have matching type and description, so keyring_compare_object() returns true. s_n_k() then passes the key to the iterator function - keyring_detect_cycle_iterator() - which *should* check to see whether this is the keyring of interest, not just one with the same name. Because assoc_array_find() will return one and only one match, I assumed that the iterator function would only see an exact match or never be called - but the iterator isn't only called from assoc_array_find()... The oops looks something like this: kernel BUG at /data/fs/linux-2.6-fscache/security/keys/keyring.c:1003! invalid opcode: 0000 [#1] SMP ... RIP: 0010:[<ffffffff811d39c3>] keyring_detect_cycle_iterator+0xe/0x1f ... Stack: ... Call Trace: [<ffffffff811d3706>] search_nested_keyrings+0x76/0x2aa [<ffffffff810fa7f4>] ? kmem_cache_alloc_trace+0xdd/0x159 [<ffffffff81235669>] ? assoc_array_insert+0xab/0x929 [<ffffffff811e226d>] ? selinux_key_permission+0x2d/0x2f [<ffffffff811dc94c>] ? security_key_permission+0x11/0x13 [<ffffffff811d3e36>] __key_link_check_live_key+0x50/0x5f [<ffffffff811d39b5>] ? keyring_describe+0x7b/0x7b [<ffffffff811d3f2b>] key_link+0x4e/0x85 [<ffffffff811d463a>] keyctl_keyring_link+0x60/0x81 [<ffffffff811d553d>] SyS_keyctl+0x65/0xe4 [<ffffffff81452edb>] tracesys+0xdd/0xe2 The fix is to make keyring_detect_cycle_iterator() check that the key it has is the key it was actually looking for rather than calling BUG_ON(). A testcase has been included in the keyutils testsuite for this: http://git.kernel.org/cgit/linux/kernel/git/dhowells/keyutils.git/commit/?id=891f3365d07f1996778ade0e3428f01878a1790b Reported-by: Tommi Rantala <tt.rantala@xxxxxxxxx> Signed-off-by: David Howells <dhowells@xxxxxxxxxx> --- diff --git a/security/keys/keyring.c b/security/keys/keyring.c index d46cbc5e335e..2fb2576dc644 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -1000,7 +1000,11 @@ static int keyring_detect_cycle_iterator(const void *object, kenter("{%d}", key->serial); - BUG_ON(key != ctx->match_data); + /* We might get a keyring with matching index-key that is nonetheless a + * different keyring. */ + if (key != ctx->match_data) + return 0; + ctx->result = ERR_PTR(-EDEADLK); return 1; } -- To unsubscribe from this list: send the line "unsubscribe trinity" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
