linux/net/netlink
Daniel Borkmann 1853c94964 netlink, mmap: transform mmap skb into full skb on taps
Ken-ichirou reported that running netlink in mmap mode for receive in
combination with nlmon will throw a NULL pointer dereference in
__kfree_skb() on nlmon_xmit(), in my case I can also trigger an "unable
to handle kernel paging request". The problem is the skb_clone() in
__netlink_deliver_tap_skb() for skbs that are mmaped.

I.e. the cloned skb doesn't have a destructor, whereas the mmap netlink
skb has it pointed to netlink_skb_destructor(), set in the handler
netlink_ring_setup_skb(). There, skb->head is being set to NULL, so
that in such cases, __kfree_skb() doesn't perform a skb_release_data()
via skb_release_all(), where skb->head is possibly being freed through
kfree(head) into slab allocator, although netlink mmap skb->head points
to the mmap buffer. Similarly, the same has to be done also for large
netlink skbs where the data area is vmalloced. Therefore, as discussed,
make a copy for these rather rare cases for now. This fixes the issue
on my and Ken-ichirou's test-cases.

Reference: http://thread.gmane.org/gmane.linux.network/371129
Fixes: bcbde0d449 ("net: netlink: virtual tap device management")
Reported-by: Ken-ichirou MATSUZAWA <chamaken@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Ken-ichirou MATSUZAWA <chamaken@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-11 14:36:49 -07:00
..
af_netlink.c netlink, mmap: transform mmap skb into full skb on taps 2015-09-11 14:36:49 -07:00
af_netlink.h netlink, mmap: transform mmap skb into full skb on taps 2015-09-11 14:36:49 -07:00
diag.c netlink: make nlmsg_end() and genlmsg_end() void 2015-01-18 01:03:45 -05:00
genetlink.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2015-01-27 16:59:56 -08:00
Kconfig netlink: kconfig: move mmap i/o into netlink kconfig 2013-05-01 15:02:42 -04:00
Makefile netlink: Diag core and basic socket info dumping (v2) 2013-03-21 12:38:03 -04:00