net: cxgb4/ch_ipsec: fix potential use-after-free in ch_ipsec_xfrm_add_state() callback

In ch_ipsec_xfrm_add_state() there is not check of try_module_get
return value. It is very unlikely, but try_module_get() could return
false value, which could cause use-after-free error.
Conditions: The module count must be zero, and a module unload in
progress. The thread doing the unload is blocked somewhere.
Another thread makes a callback into the module for some request
that (for instance) would need to create a kernel thread.
It tries to get a reference for the thread.
So try_module_get(THIS_MODULE) is the right call - and will fail here.

This fix adds checking the result of try_module_get call

Fixes: 6dad4e8 ("chcr: Add support for Inline IPSec")
Signed-off-by: Pavel Zhigulin <Pavel.Zhigulin@kaspersky.com>
Link: https://patch.msgid.link/20251024161304.724436-1-Pavel.Zhigulin@kaspersky.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Pavel Zhigulin

drivers/net/ethernet/chelsio/inline_crypto/ch_ipsec/chcr_ipsec.c

@@ -290,9 +290,15 @@ static int ch_ipsec_xfrm_add_state(struct net_device *dev,
 		return -EINVAL;
 	}
 
+	if (unlikely(!try_module_get(THIS_MODULE))) {
+		NL_SET_ERR_MSG_MOD(extack, "Failed to acquire module reference");
+		return -ENODEV;
+	}
+
 	sa_entry = kzalloc(sizeof(*sa_entry), GFP_KERNEL);
 	if (!sa_entry) {
 		res = -ENOMEM;
+		module_put(THIS_MODULE);
 		goto out;
 	}
 
@@ -301,7 +307,6 @@ static int ch_ipsec_xfrm_add_state(struct net_device *dev,
 		sa_entry->esn = 1;
 	ch_ipsec_setkey(x, sa_entry);
 	x->xso.offload_handle = (unsigned long)sa_entry;
-	try_module_get(THIS_MODULE);
 out:
 	return res;
 }