From ed42989eab57d619667d7e87dfbd8fe207db54fe Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Wed, 7 Oct 2020 21:12:50 -0700 Subject: tipc: fix the skb_unshare() in tipc_buf_append() 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 Cc: Ying Xue Signed-off-by: Cong Wang Reviewed-by: Xin Long Signed-off-by: Jakub Kicinski --- net/tipc/msg.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/tipc') diff --git a/net/tipc/msg.c b/net/tipc/msg.c index 52e93ba4d8e2..681224401871 100644 --- a/net/tipc/msg.c +++ b/net/tipc/msg.c @@ -150,7 +150,8 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf) if (fragid == FIRST_FRAGMENT) { if (unlikely(head)) goto err; - frag = skb_unshare(frag, GFP_ATOMIC); + if (skb_cloned(frag)) + frag = skb_copy(frag, GFP_ATOMIC); if (unlikely(!frag)) goto err; head = *headbuf = frag; -- cgit v1.2.3-70-g09d2 From 7b50ee3dad2581dc022b4e32e55964d4fcdccf20 Mon Sep 17 00:00:00 2001 From: Hoang Huu Le Date: Thu, 8 Oct 2020 14:31:56 +0700 Subject: tipc: fix NULL pointer dereference in tipc_named_rcv In the function node_lost_contact(), we call __skb_queue_purge() without grabbing the list->lock. This can cause to a race-condition why processing the list 'namedq' in calling path tipc_named_rcv()->tipc_named_dequeue(). [] BUG: kernel NULL pointer dereference, address: 0000000000000000 [] #PF: supervisor read access in kernel mode [] #PF: error_code(0x0000) - not-present page [] PGD 7ca63067 P4D 7ca63067 PUD 6c553067 PMD 0 [] Oops: 0000 [#1] SMP NOPTI [] CPU: 1 PID: 15 Comm: ksoftirqd/1 Tainted: G O 5.9.0-rc6+ #2 [] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS [...] [] RIP: 0010:tipc_named_rcv+0x103/0x320 [tipc] [] Code: 41 89 44 24 10 49 8b 16 49 8b 46 08 49 c7 06 00 00 00 [...] [] RSP: 0018:ffffc900000a7c58 EFLAGS: 00000282 [] RAX: 00000000000012ec RBX: 0000000000000000 RCX: ffff88807bde1270 [] RDX: 0000000000002c7c RSI: 0000000000002c7c RDI: ffff88807b38f1a8 [] RBP: ffff88807b006288 R08: ffff88806a367800 R09: ffff88806a367900 [] R10: ffff88806a367a00 R11: ffff88806a367b00 R12: ffff88807b006258 [] R13: ffff88807b00628a R14: ffff888069334d00 R15: ffff88806a434600 [] FS: 0000000000000000(0000) GS:ffff888079480000(0000) knlGS:0[...] [] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [] CR2: 0000000000000000 CR3: 0000000077320000 CR4: 00000000000006e0 [] Call Trace: [] ? tipc_bcast_rcv+0x9a/0x1a0 [tipc] [] tipc_rcv+0x40d/0x670 [tipc] [] ? _raw_spin_unlock+0xa/0x20 [] tipc_l2_rcv_msg+0x55/0x80 [tipc] [] __netif_receive_skb_one_core+0x8c/0xa0 [] process_backlog+0x98/0x140 [] net_rx_action+0x13a/0x420 [] __do_softirq+0xdb/0x316 [] ? smpboot_thread_fn+0x2f/0x1e0 [] ? smpboot_thread_fn+0x74/0x1e0 [] ? smpboot_thread_fn+0x14e/0x1e0 [] run_ksoftirqd+0x1a/0x40 [] smpboot_thread_fn+0x149/0x1e0 [] ? sort_range+0x20/0x20 [] kthread+0x131/0x150 [] ? kthread_unuse_mm+0xa0/0xa0 [] ret_from_fork+0x22/0x30 [] Modules linked in: veth tipc(O) ip6_udp_tunnel udp_tunnel [...] [] CR2: 0000000000000000 [] ---[ end trace 65c276a8e2e2f310 ]--- To fix this, we need to grab the lock of the 'namedq' list on both path calling. Fixes: cad2929dc432 ("tipc: update a binding service via broadcast") Acked-by: Jon Maloy Signed-off-by: Hoang Huu Le Signed-off-by: Jakub Kicinski --- net/tipc/name_distr.c | 10 +++++++++- net/tipc/node.c | 2 +- 2 files changed, 10 insertions(+), 2 deletions(-) (limited to 'net/tipc') diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c index 2f9c148f17e2..fe4edce459ad 100644 --- a/net/tipc/name_distr.c +++ b/net/tipc/name_distr.c @@ -327,8 +327,13 @@ static struct sk_buff *tipc_named_dequeue(struct sk_buff_head *namedq, struct tipc_msg *hdr; u16 seqno; + spin_lock_bh(&namedq->lock); skb_queue_walk_safe(namedq, skb, tmp) { - skb_linearize(skb); + if (unlikely(skb_linearize(skb))) { + __skb_unlink(skb, namedq); + kfree_skb(skb); + continue; + } hdr = buf_msg(skb); seqno = msg_named_seqno(hdr); if (msg_is_last_bulk(hdr)) { @@ -338,12 +343,14 @@ static struct sk_buff *tipc_named_dequeue(struct sk_buff_head *namedq, if (msg_is_bulk(hdr) || msg_is_legacy(hdr)) { __skb_unlink(skb, namedq); + spin_unlock_bh(&namedq->lock); return skb; } if (*open && (*rcv_nxt == seqno)) { (*rcv_nxt)++; __skb_unlink(skb, namedq); + spin_unlock_bh(&namedq->lock); return skb; } @@ -353,6 +360,7 @@ static struct sk_buff *tipc_named_dequeue(struct sk_buff_head *namedq, continue; } } + spin_unlock_bh(&namedq->lock); return NULL; } diff --git a/net/tipc/node.c b/net/tipc/node.c index 4edcee3088da..e4cf515e323f 100644 --- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -1485,7 +1485,7 @@ static void node_lost_contact(struct tipc_node *n, /* Clean up broadcast state */ tipc_bcast_remove_peer(n->net, n->bc_entry.link); - __skb_queue_purge(&n->bc_entry.namedq); + skb_queue_purge(&n->bc_entry.namedq); /* Abort any ongoing link failover */ for (i = 0; i < MAX_BEARERS; i++) { -- cgit v1.2.3-70-g09d2