[PATCH] Bluetooth: bnep: Fix UAF read of dev->name

[PATCH] Bluetooth: bnep: Fix UAF read of dev->name

[Jann Horn]

bnep_add_connection() needs to keep holding the bnep_session_sem while
reading dev->name (just like bnep_get_connlist() does); otherwise the
bnep_session() thread can concurrently free the net_device, which can for
example be triggered by a concurrent bnep_del_connection().

(This UAF is fairly uninteresting from a security perspective;
calling bnep_add_connection() requires passing a capable(CAP_NET_ADMIN)
check. It also requires completely tearing down a netdev during a fairly
tight race window.)

Cc: stable@vger.kernel.org
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jann Horn <jannh@google.com>
---
I have tested that this bug can lead to UAF by using KASAN and
introducing an artificial delay with mdelay().
---
 net/bluetooth/bnep/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index 853c8d7644b5..0de5df690bd0 100644
--- a/net/bluetooth/bnep/core.c
+++ b/net/bluetooth/bnep/core.c
@@ -645,8 +645,8 @@ int bnep_add_connection(struct bnep_connadd_req *req, struct socket *sock)
 		goto failed;
 	}
 
-	up_write(&bnep_session_sem);
 	strcpy(req->device, dev->name);
+	up_write(&bnep_session_sem);
 	return 0;
 
 failed:

---
base-commit: 1d5dcaa3bd65f2e8c9baa14a393d3a2dc5db7524
change-id: 20260512-bnep-add-uaf-f730caec3b13

--  
Jann Horn <jannh@google.com>

Re: [PATCH] Bluetooth: bnep: Fix UAF read of dev->name

[patchwork-bot+bluetooth]

Hello:

This patch was applied to bluetooth/bluetooth-next.git (master)
by Luiz Augusto von Dentz <luiz.von.dentz@intel.com>:

On Tue, 12 May 2026 22:15:39 +0200 you wrote:
> bnep_add_connection() needs to keep holding the bnep_session_sem while
> reading dev->name (just like bnep_get_connlist() does); otherwise the
> bnep_session() thread can concurrently free the net_device, which can for
> example be triggered by a concurrent bnep_del_connection().
> 
> (This UAF is fairly uninteresting from a security perspective;
> calling bnep_add_connection() requires passing a capable(CAP_NET_ADMIN)
> check. It also requires completely tearing down a netdev during a fairly
> tight race window.)
> 
> [...]

Here is the summary with links:
  - Bluetooth: bnep: Fix UAF read of dev->name
    https://git.kernel.org/bluetooth/bluetooth-next/c/ffeee619a13b

You are awesome, thank you!
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