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authorXin Long <lucien.xin@gmail.com>2021-05-08 03:57:03 +0800
committerDavid S. Miller <davem@davemloft.net>2021-05-17 13:42:17 -0700
commitb7df21cf1b79ab7026f545e7bf837bd5750ac026 (patch)
tree5b8bca0e2084c9b5ddd967cd74354e6914db63a2 /net/tipc
parentb81ac7841d511d68989534eff5550269e1bf896d (diff)
tipc: skb_linearize the head skb when reassembling msgs
It's not a good idea to append the frag skb to a skb's frag_list if the frag_list already has skbs from elsewhere, such as this skb was created by pskb_copy() where the frag_list was cloned (all the skbs in it were skb_get'ed) and shared by multiple skbs. However, the new appended frag skb should have been only seen by the current skb. Otherwise, it will cause use after free crashes as this appended frag skb are seen by multiple skbs but it only got skb_get called once. The same thing happens with a skb updated by pskb_may_pull() with a skb_cloned skb. Li Shuang has reported quite a few crashes caused by this when doing testing over macvlan devices: [] kernel BUG at net/core/skbuff.c:1970! [] Call Trace: [] skb_clone+0x4d/0xb0 [] macvlan_broadcast+0xd8/0x160 [macvlan] [] macvlan_process_broadcast+0x148/0x150 [macvlan] [] process_one_work+0x1a7/0x360 [] worker_thread+0x30/0x390 [] kernel BUG at mm/usercopy.c:102! [] Call Trace: [] __check_heap_object+0xd3/0x100 [] __check_object_size+0xff/0x16b [] simple_copy_to_iter+0x1c/0x30 [] __skb_datagram_iter+0x7d/0x310 [] __skb_datagram_iter+0x2a5/0x310 [] skb_copy_datagram_iter+0x3b/0x90 [] tipc_recvmsg+0x14a/0x3a0 [tipc] [] ____sys_recvmsg+0x91/0x150 [] ___sys_recvmsg+0x7b/0xc0 [] kernel BUG at mm/slub.c:305! [] Call Trace: [] <IRQ> [] kmem_cache_free+0x3ff/0x400 [] __netif_receive_skb_core+0x12c/0xc40 [] ? kmem_cache_alloc+0x12e/0x270 [] netif_receive_skb_internal+0x3d/0xb0 [] ? get_rx_page_info+0x8e/0xa0 [be2net] [] be_poll+0x6ef/0xd00 [be2net] [] ? irq_exit+0x4f/0x100 [] net_rx_action+0x149/0x3b0 ... This patch is to fix it by linearizing the head skb if it has frag_list set in tipc_buf_append(). Note that we choose to do this before calling skb_unshare(), as __skb_linearize() will avoid skb_copy(). Also, we can not just drop the frag_list either as the early time. Fixes: 45c8b7b175ce ("tipc: allow non-linear first fragment buffer") Reported-by: Li Shuang <shuali@redhat.com> Signed-off-by: Xin Long <lucien.xin@gmail.com> Acked-by: Jon Maloy <jmaloy@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc')
-rw-r--r--net/tipc/msg.c9
1 files changed, 2 insertions, 7 deletions
diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index 3f0a25345a7c..ce6ab54822d8 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -149,18 +149,13 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf)
if (unlikely(head))
goto err;
*buf = NULL;
+ if (skb_has_frag_list(frag) && __skb_linearize(frag))
+ goto err;
frag = skb_unshare(frag, GFP_ATOMIC);
if (unlikely(!frag))
goto err;
head = *headbuf = frag;
TIPC_SKB_CB(head)->tail = NULL;
- if (skb_is_nonlinear(head)) {
- skb_walk_frags(head, tail) {
- TIPC_SKB_CB(head)->tail = tail;
- }
- } else {
- skb_frag_list_init(head);
- }
return 0;
}