[ Upstream commit ceb1eb2fb609c88363e06618b8d4bbf7815a4e03 ]
Commit ed42989eab57 ("tipc: fix the skb_unshare() in tipc_buf_append()")
replaced skb_unshare() with skb_copy() to not reduce the data reference
counter of the original skb intentionally. This is not the correct
way to handle the cloned skb because it causes memory leak in 2
following cases:
1/ Sending multicast messages via broadcast link
The original skb list is cloned to the local skb list for local
destination. After that, the data reference counter of each skb
in the original list has the value of 2. This causes each skb not
to be freed after receiving ACK:
tipc_link_advance_transmq()
{
...
/* release skb */
__skb_unlink(skb, &l->transmq);
kfree_skb(skb); <-- memory exists after being freed
}
2/ Sending multicast messages via replicast link
Similar to the above case, each skb cannot be freed after purging
the skb list:
tipc_mcast_xmit()
{
...
__skb_queue_purge(pkts); <-- memory exists after being freed
}
This commit fixes this issue by using skb_unshare() instead. Besides,
to avoid use-after-free error reported by KASAN, the pointer to the
fragment is set to NULL before calling skb_unshare() to make sure that
the original skb is not freed after freeing the fragment 2 times in
case skb_unshare() returns NULL.
Fixes: ed42989eab57 ("tipc: fix the skb_unshare() in tipc_buf_append()")
Acked-by: Jon Maloy <jmaloy@redhat.com>
Reported-by: Thang Hoang Ngo <thang.h.ngo@dektech.com.au>
Signed-off-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Link: https://lore.kernel.org/r/20201027032403.1823-1-tung.q.nguyen@dektech.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit ed42989eab57d619667d7e87dfbd8fe207db54fe ]
skb_unshare() drops a reference count on the old skb unconditionally,
so in the failure case, we end up freeing the skb twice here.
And because the skb is allocated in fclone and cloned by caller
tipc_msg_reassemble(), the consequence is actually freeing the
original skb too, thus triggered the UAF by syzbot.
Fix this by replacing this skb_unshare() with skb_cloned()+skb_copy().
Fixes: ff48b6222e65 ("tipc: use skb_unshare() instead in tipc_buf_append()")
Reported-and-tested-by: syzbot+e96a7ba46281824cc46a@syzkaller.appspotmail.com
Cc: Jon Maloy <jmaloy@redhat.com>
Cc: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit ff48b6222e65ebdba5a403ef1deba6214e749193 ]
In tipc_buf_append() it may change skb's frag_list, and it causes
problems when this skb is cloned. skb_unclone() doesn't really
make this skb's flag_list available to change.
Shuang Li has reported an use-after-free issue because of this
when creating quite a few macvlan dev over the same dev, where
the broadcast packets will be cloned and go up to the stack:
[ ] BUG: KASAN: use-after-free in pskb_expand_head+0x86d/0xea0
[ ] Call Trace:
[ ] dump_stack+0x7c/0xb0
[ ] print_address_description.constprop.7+0x1a/0x220
[ ] kasan_report.cold.10+0x37/0x7c
[ ] check_memory_region+0x183/0x1e0
[ ] pskb_expand_head+0x86d/0xea0
[ ] process_backlog+0x1df/0x660
[ ] net_rx_action+0x3b4/0xc90
[ ]
[ ] Allocated by task 1786:
[ ] kmem_cache_alloc+0xbf/0x220
[ ] skb_clone+0x10a/0x300
[ ] macvlan_broadcast+0x2f6/0x590 [macvlan]
[ ] macvlan_process_broadcast+0x37c/0x516 [macvlan]
[ ] process_one_work+0x66a/0x1060
[ ] worker_thread+0x87/0xb10
[ ]
[ ] Freed by task 3253:
[ ] kmem_cache_free+0x82/0x2a0
[ ] skb_release_data+0x2c3/0x6e0
[ ] kfree_skb+0x78/0x1d0
[ ] tipc_recvmsg+0x3be/0xa40 [tipc]
So fix it by using skb_unshare() instead, which would create a new
skb for the cloned frag and it'll be safe to change its frag_list.
The similar things were also done in sctp_make_reassembled_event(),
which is using skb_copy().
Reported-by: Shuang Li <shuali@redhat.com>
Fixes: 37e22164a8a3 ("tipc: rename and move message reassembly function")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tung Nguyen