[PATCH 5.14 782/849] net/smc: fix sk_refcnt underflow on linkdown and fallback

Greg Kroah-Hartman
2021-11-16T01:16:33Z

From: Dust Li <dust.li@linux.alibaba.com>

[ Upstream commit e5d5aadcf3cd59949316df49c27cb21788d7efe4 ]

We got the following WARNING when running ab/nginx
test with RDMA link flapping (up-down-up).
The reason is when smc_sock fallback and at linkdown
happens simultaneously, we may got the following situation:

__smc_lgr_terminate()
--> smc_conn_kill()
--> smc_close_active_abort()
smc_sock->sk_state = SMC_CLOSED
sock_put(smc_sock)

smc_sock was set to SMC_CLOSED and sock_put() been called
when terminate the link group. But later application call
close() on the socket, then we got:

__smc_release():
if (smc_sock->fallback)
smc_sock->sk_state = SMC_CLOSED
sock_put(smc_sock)

Again we set the smc_sock to CLOSED through it's already
in CLOSED state, and double put the refcnt, so the following
warning happens:

refcount_t: underflow; use-after-free.
WARNING: CPU: 5 PID: 860 at lib/refcount.c:28 refcount_warn_saturate+0x8d/0xf0
Modules linked in:
CPU: 5 PID: 860 Comm: nginx Not tainted 5.10.46+ #403
Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 8c24b4c 04/01/2014
RIP: 0010:refcount_warn_saturate+0x8d/0xf0
Code: 05 5c 1e b5 01 01 e8 52 25 bc ff 0f 0b c3 80 3d 4f 1e b5 01 00 75 ad 48

RSP: 0018:ffffc90000527e50 EFLAGS: 00010286
RAX: 0000000000000026 RBX: ffff8881300df2c0 RCX: 0000000000000027
RDX: 0000000000000000 RSI: ffff88813bd58040 RDI: ffff88813bd58048
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000001
R10: ffff8881300df2c0 R11: ffffc90000527c78 R12: ffff8881300df340
R13: ffff8881300df930 R14: ffff88810b3dad80 R15: ffff8881300df4f8
FS: 00007f739de8fb80(0000) GS:ffff88813bd40000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000a01b008 CR3: 0000000111b64003 CR4: 00000000003706e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
smc_release+0x353/0x3f0
__sock_release+0x3d/0xb0
sock_close+0x11/0x20
__fput+0x93/0x230
task_work_run+0x65/0xa0
exit_to_user_mode_prepare+0xf9/0x100
syscall_exit_to_user_mode+0x27/0x190
entry_SYSCALL_64_after_hwframe+0x44/0xa9

This patch adds check in __smc_release() to make
sure we won't do an extra sock_put() and set the
socket to CLOSED when its already in CLOSED state.

Fixes: 51f1de79ad8e (net/smc: replace sock_put worker by socket refcounting)
Signed-off-by: Dust Li <dust.li@linux.alibaba.com>
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: Dust Li <dust.li@linux.alibaba.com>
Acked-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/smc/af_smc.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 78b663dbfa1f9..32c1c7ce856d3 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -148,14 +148,18 @@ static int __smc_release(struct smc_sock *smc)
sock_set_flag(sk, SOCK_DEAD);
sk->sk_shutdown |= SHUTDOWN_MASK;
} else {
- if (sk->sk_state != SMC_LISTEN && sk->sk_state != SMC_INIT)
- sock_put(sk); /* passive closing */
- if (sk->sk_state == SMC_LISTEN) {
- /* wake up clcsock accept */
- rc = kernel_sock_shutdown(smc->clcsock, SHUT_RDWR);
+ if (sk->sk_state != SMC_CLOSED) {
+ if (sk->sk_state != SMC_LISTEN &&
+ sk->sk_state != SMC_INIT)
+ sock_put(sk); /* passive closing */
+ if (sk->sk_state == SMC_LISTEN) {
+ /* wake up clcsock accept */
+ rc = kernel_sock_shutdown(smc->clcsock,
+ SHUT_RDWR);
+ }
+ sk->sk_state = SMC_CLOSED;
+ sk->sk_state_change(sk);
}
- sk->sk_state = SMC_CLOSED;
- sk->sk_state_change(sk);
smc_restore_fallback_changes(smc);
}

--
2.33.0