[PATCH 4/5] RDMA/siw: Set siw_crypto_shash to NULL after it is freed

[Guoqing Jiang <guoqing.jiang@linux.dev>]

In case siw module can't be inserted successfully, then remove the
module from kernel, which means both siw_cm_exit and the failure
path in siw_init_module call crypto_free_shash. We can see below
call trace appears.

[   72.349344] ------------[ cut here ]------------
[   72.349348] refcount_t: underflow; use-after-free.
[   72.349386] WARNING: CPU: 1 PID: 1737 at lib/refcount.c:28 refcount_warn_saturate+0xfb/0x150
...
[   72.349469] RIP: 0010:refcount_warn_saturate+0xfb/0x150
...
[   72.349487] Call Trace:
[   72.349488]  <TASK>
[   72.349490]  ? show_regs+0x72/0x90
[   72.349493]  ? refcount_warn_saturate+0xfb/0x150
[   72.349495]  ? __warn+0x8d/0x1a0
[   72.349498]  ? refcount_warn_saturate+0xfb/0x150
[   72.349500]  ? report_bug+0x1f9/0x250
[   72.349505]  ? handle_bug+0x46/0x90
[   72.349508]  ? exc_invalid_op+0x19/0x80
[   72.349511]  ? asm_exc_invalid_op+0x1b/0x20
[   72.349517]  ? refcount_warn_saturate+0xfb/0x150
[   72.349519]  ? refcount_warn_saturate+0xfb/0x150
[   72.349521]  crypto_destroy_tfm+0x9b/0xe0
[   72.349525]  siw_exit_module+0xf6/0x590 [siw]

So we need to set siw_crypto_shash to null in the failure path of
siw_init_module.

Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
---
 drivers/infiniband/sw/siw/siw_main.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/sw/siw/siw_main.c b/drivers/infiniband/sw/siw/siw_main.c
index 6709ed0de3a4..f8549d01887f 100644
--- a/drivers/infiniband/sw/siw/siw_main.c
+++ b/drivers/infiniband/sw/siw/siw_main.c
@@ -589,8 +589,10 @@ static __init int siw_init_module(void)
 			siw_tx_thread[nr_cpu] = NULL;
 		}
 	}
-	if (siw_crypto_shash)
+	if (siw_crypto_shash) {
 		crypto_free_shash(siw_crypto_shash);
+		siw_crypto_shash = NULL;
+	}
 
 	pr_info("SoftIWARP attach failed. Error: %d\n", rv);
 
-- 
2.34.1