[PATCH 5.9 018/757] tipc: fix NULL pointer dereference in tipc_named_rcv

Greg Kroah-Hartman
2020-10-27T15:58:52Z

From: Hoang Huu Le <hoang.h.le@dektech.com.au>

[ Upstream commit 7b50ee3dad2581dc022b4e32e55964d4fcdccf20 ]

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 <jmaloy@redhat.com>
Signed-off-by: Hoang Huu Le <hoang.h.le@dektech.com.au>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/tipc/name_distr.c | 10 +++++++++-
net/tipc/node.c | 2 +-
2 files changed, 10 insertions(+), 2 deletions(-)

--- a/net/tipc/name_distr.c
+++ b/net/tipc/name_distr.c
@@ -327,8 +327,13 @@ static struct sk_buff *tipc_named_dequeu
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_dequeu

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_dequeu
continue;
}
}
+ spin_unlock_bh(&namedq->lock);
return NULL;
}

--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -1485,7 +1485,7 @@ static void node_lost_contact(struct tip

/* 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++) {