Acked-by: James Morris <[email protected]>
On Tue, 4 Mar 2014, David Howells wrote: > > 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 <[email protected]> > Signed-off-by: David Howells <[email protected]> > --- > 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 > linux-security-module" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- James Morris <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
