This is a note to let you know that I've just added the patch titled
net/smc: fix LGR and link use-after-free issue
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-smc-fix-lgr-and-link-use-after-free-issue.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7510ba86773185e342545903770f1f0be0813dfc
Author: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
Date: Wed Nov 27 21:30:14 2024 +0800
net/smc: fix LGR and link use-after-free issue
[ Upstream commit 2c7f14ed9c19ec0f149479d1c2842ec1f9bf76d7 ]
We encountered a LGR/link use-after-free issue, which manifested as
the LGR/link refcnt reaching 0 early and entering the clear process,
making resource access unsafe.
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 14 PID: 107447 at lib/refcount.c:25 refcount_warn_saturate+0x9c/0x140
Workqueue: events smc_lgr_terminate_work [smc]
Call trace:
refcount_warn_saturate+0x9c/0x140
__smc_lgr_terminate.part.45+0x2a8/0x370 [smc]
smc_lgr_terminate_work+0x28/0x30 [smc]
process_one_work+0x1b8/0x420
worker_thread+0x158/0x510
kthread+0x114/0x118
or
refcount_t: underflow; use-after-free.
WARNING: CPU: 6 PID: 93140 at lib/refcount.c:28 refcount_warn_saturate+0xf0/0x140
Workqueue: smc_hs_wq smc_listen_work [smc]
Call trace:
refcount_warn_saturate+0xf0/0x140
smcr_link_put+0x1cc/0x1d8 [smc]
smc_conn_free+0x110/0x1b0 [smc]
smc_conn_abort+0x50/0x60 [smc]
smc_listen_find_device+0x75c/0x790 [smc]
smc_listen_work+0x368/0x8a0 [smc]
process_one_work+0x1b8/0x420
worker_thread+0x158/0x510
kthread+0x114/0x118
It is caused by repeated release of LGR/link refcnt. One suspect is that
smc_conn_free() is called repeatedly because some smc_conn_free() from
server listening path are not protected by sock lock.
e.g.
Calls under socklock | smc_listen_work
-------------------------------------------------------
lock_sock(sk) | smc_conn_abort
smc_conn_free | \- smc_conn_free
\- smcr_link_put | \- smcr_link_put (duplicated)
release_sock(sk)
So here add sock lock protection in smc_listen_work() path, making it
exclusive with other connection operations.
Fixes: 3b2dec2603d5 ("net/smc: restructure client and server code in af_smc")
Co-developed-by: Guangguan Wang <guangguan.wang@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guangguan Wang <guangguan.wang@xxxxxxxxxxxxxxxxx>
Co-developed-by: Kai <KaiShen@xxxxxxxxxxxxxxxxx>
Signed-off-by: Kai <KaiShen@xxxxxxxxxxxxxxxxx>
Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
Reviewed-by: Wenjia Zhang <wenjia@xxxxxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 755659703a625..77c6c0dff069e 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1907,6 +1907,7 @@ static void smc_listen_out(struct smc_sock *new_smc)
if (tcp_sk(new_smc->clcsock->sk)->syn_smc)
atomic_dec(&lsmc->queued_smc_hs);
+ release_sock(newsmcsk); /* lock in smc_listen_work() */
if (lsmc->sk.sk_state == SMC_LISTEN) {
lock_sock_nested(&lsmc->sk, SINGLE_DEPTH_NESTING);
smc_accept_enqueue(&lsmc->sk, newsmcsk);
@@ -2428,6 +2429,7 @@ static void smc_listen_work(struct work_struct *work)
u8 accept_version;
int rc = 0;
+ lock_sock(&new_smc->sk); /* release in smc_listen_out() */
if (new_smc->listen_smc->sk.sk_state != SMC_LISTEN)
return smc_listen_out_err(new_smc);
