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SubjectRe: [PATCH net] net/smc: fix illegal rmb_desc access in SMC-D connection dump
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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@linux.alibaba.com>
>> ---
>> 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

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