Re: [PATCH net] net/smc: fix illegal rmb_desc access in SMC-D connection dump
From: Wen Gu
Date: Wed Jan 17 2024 - 21:07:37 EST
On 2024/1/18 09:50, Dust Li wrote:
On Wed, Jan 17, 2024 at 08:27:49PM +0800, Wen Gu wrote:
A crash was found when dumping SMC-D connections. It can be reproduced
by following steps:
- run nginx/wrk test:
smc_run nginx
smc_run wrk -t 16 -c 1000 -d <duration> -H 'Connection: Close' <URL>
- continuously dump SMC-D connections in parallel:
watch -n 1 'smcss -D'
BUG: kernel NULL pointer dereference, address: 0000000000000030
CPU: 2 PID: 7204 Comm: smcss Kdump: loaded Tainted: G E 6.7.0+ #55
RIP: 0010:__smc_diag_dump.constprop.0+0x5e5/0x620 [smc_diag]
Call Trace:
<TASK>
? __die+0x24/0x70
? page_fault_oops+0x66/0x150
? exc_page_fault+0x69/0x140
? asm_exc_page_fault+0x26/0x30
? __smc_diag_dump.constprop.0+0x5e5/0x620 [smc_diag]
? __kmalloc_node_track_caller+0x35d/0x430
? __alloc_skb+0x77/0x170
smc_diag_dump_proto+0xd0/0xf0 [smc_diag]
smc_diag_dump+0x26/0x60 [smc_diag]
netlink_dump+0x19f/0x320
__netlink_dump_start+0x1dc/0x300
smc_diag_handler_dump+0x6a/0x80 [smc_diag]
? __pfx_smc_diag_dump+0x10/0x10 [smc_diag]
sock_diag_rcv_msg+0x121/0x140
? __pfx_sock_diag_rcv_msg+0x10/0x10
netlink_rcv_skb+0x5a/0x110
sock_diag_rcv+0x28/0x40
netlink_unicast+0x22a/0x330
netlink_sendmsg+0x1f8/0x420
__sock_sendmsg+0xb0/0xc0
____sys_sendmsg+0x24e/0x300
? copy_msghdr_from_user+0x62/0x80
___sys_sendmsg+0x7c/0xd0
? __do_fault+0x34/0x160
? do_read_fault+0x5f/0x100
? do_fault+0xb0/0x110
? __handle_mm_fault+0x2b0/0x6c0
__sys_sendmsg+0x4d/0x80
do_syscall_64+0x69/0x180
entry_SYSCALL_64_after_hwframe+0x6e/0x76
It is possible that the connection is in process of being established
when we dump it. Assumed that the connection has been registered in a
link group by smc_conn_create() but the rmb_desc has not yet been
initialized by smc_buf_create(), thus causing the illegal access to
conn->rmb_desc. So fix it by checking before dump.
Fixes: ce51f63e63c5 ("net/smc: Prevent kernel-infoleak in __smc_diag_dump()")
ce51f63e63c5 ("net/smc: Prevent kernel-infoleak in __smc_diag_dump()")
only add a memset() of 'struct smcd_diag_dmbinfo dinfo', which I don't
think is not the real cause of the bug.
After re-checking the definition of Fixes tag, I agree that
ce51f63e63c5 is not appropriate and
4b1b7d3b30a6 ("net/smc: add SMC-D diag support") should be used.
Thank you!
Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
---
net/smc/smc_diag.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/smc/smc_diag.c b/net/smc/smc_diag.c
index 52f7c4f1e767..5a33908015f3 100644
--- a/net/smc/smc_diag.c
+++ b/net/smc/smc_diag.c
@@ -164,7 +164,7 @@ static int __smc_diag_dump(struct sock *sk, struct sk_buff *skb,
}
if (smc_conn_lgr_valid(&smc->conn) && smc->conn.lgr->is_smcd &&
(req->diag_ext & (1 << (SMC_DIAG_DMBINFO - 1))) &&
- !list_empty(&smc->conn.lgr->list)) {
+ !list_empty(&smc->conn.lgr->list) && smc->conn.rmb_desc) {
struct smc_connection *conn = &smc->conn;
struct smcd_diag_dmbinfo dinfo;
struct smcd_dev *smcd = conn->lgr->smcd;
--
2.43.0