Re: [PATCH net] net/smc: fix invalid link access in dumping SMC-R connections
From: Wen Gu
Date: Thu Dec 28 2023 - 06:03:04 EST
On 2023/12/28 17:32, Tony Lu wrote:
On Wed, Dec 27, 2023 at 03:40:35PM +0800, Wen Gu wrote:
A crash was found when dumping SMC-R connections. It can be reproduced
by following steps:
- environment: two RNICs on both sides.
- run SMC-R between two sides, now a SMC_LGR_SYMMETRIC type link group
will be created.
- set the first RNIC down on either side and link group will turn to
SMC_LGR_ASYMMETRIC_LOCAL then.
- run 'smcss -R' and the crash will be triggered.
BUG: kernel NULL pointer dereference, address: 0000000000000010
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 8000000101fdd067 P4D 8000000101fdd067 PUD 10ce46067 PMD 0
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 3 PID: 1810 Comm: smcss Kdump: loaded Tainted: G W E 6.7.0-rc6+ #51
RIP: 0010:__smc_diag_dump.constprop.0+0x36e/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+0x36e/0x620 [smc_diag]
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+0x240/0x4a0
__sock_sendmsg+0xb0/0xc0
____sys_sendmsg+0x24e/0x300
? copy_msghdr_from_user+0x62/0x80
___sys_sendmsg+0x7c/0xd0
? __do_fault+0x34/0x1a0
? do_read_fault+0x5f/0x100
? do_fault+0xb0/0x110
__sys_sendmsg+0x4d/0x80
do_syscall_64+0x45/0xf0
entry_SYSCALL_64_after_hwframe+0x6e/0x76
When the first RNIC is set down, the lgr->lnk[0] will be cleared and an
asymmetric link will be allocated in lgr->link[SMC_LINKS_PER_LGR_MAX - 1]
by smc_llc_alloc_alt_link(). Then when we try to dump SMC-R connections
in __smc_diag_dump(), the invalid lgr->lnk[0] will be accessed, resulting
in this issue. So fix it by accessing the right link.
Fixes: f16a7dd5cf27 ("smc: netlink interface for SMC sockets")
Reported-by: henaumars <henaumars@xxxxxxxx>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=7616
What about using Link: http... here?
Thank you, Tony.
According to [1],
"
The Reported-by tag gives credit to people who find bugs and report them and it
hopefully inspires them to help us again in the future. The tag is intended for
bugs; please do not use it to credit feature requests. The tag should be followed
by a Closes: tag pointing to the report, unless the report is not available on
the web. The Link: tag can be used instead of Closes: if the patch fixes a part
of the issue(s) being reported.
"
So I guess the Closes: tag is fine here.
[1] https://docs.kernel.org/process/submitting-patches.html
Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
Reviewed-by: Tony Lu <tonylu@xxxxxxxxxxxxxxxxx>
---
net/smc/smc_diag.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/net/smc/smc_diag.c b/net/smc/smc_diag.c
index a584613aca12..5cc376834c57 100644
--- a/net/smc/smc_diag.c
+++ b/net/smc/smc_diag.c
@@ -153,8 +153,7 @@ static int __smc_diag_dump(struct sock *sk, struct sk_buff *skb,
.lnk[0].link_id = link->link_id,
};
- memcpy(linfo.lnk[0].ibname,
- smc->conn.lgr->lnk[0].smcibdev->ibdev->name,
+ memcpy(linfo.lnk[0].ibname, link->smcibdev->ibdev->name,
sizeof(link->smcibdev->ibdev->name));
smc_gid_be16_convert(linfo.lnk[0].gid, link->gid);
smc_gid_be16_convert(linfo.lnk[0].peer_gid, link->peer_gid);
--
2.43.0