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From: Pauli Virtanen <pav@iki.fi>
To: linux-bluetooth@vger.kernel.org
Cc: Pauli Virtanen <pav@iki.fi>
Subject: [PATCH] Bluetooth: fix use-after-free in accessing skb after sending it
Date: Sat,  2 Mar 2024 19:06:23 +0200
Message-ID: <90576ca2ad6b1c3e24c585c734cde44bbcb388bf.1709399114.git.pav@iki.fi>
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hci_send_cmd_sync first sends skb and then tries to clone it.  However,
the driver may have already freed the skb at that point.

Fix by cloning the sent_cmd cloned just above, instead of the original.

Log:
================================================================
BUG: KASAN: slab-use-after-free in __copy_skb_header+0x1a/0x240
...
Call Trace: ..
 __skb_clone+0x59/0x2c0
 hci_cmd_work+0x3b3/0x3d0 [bluetooth]
 process_one_work+0x459/0x900
...
Allocated by task 129: ...
 __alloc_skb+0x1ae/0x220
 __hci_cmd_sync_sk+0x44c/0x7a0 [bluetooth]
 __hci_cmd_sync_status+0x24/0xb0 [bluetooth]
 set_cig_params_sync+0x778/0x7d0 [bluetooth]
...
Freed by task 0: ...
 kmem_cache_free+0x157/0x3c0
 __usb_hcd_giveback_urb+0x11e/0x1e0
 usb_giveback_urb_bh+0x1ad/0x2a0
 tasklet_action_common.isra.0+0x259/0x4a0
 __do_softirq+0x15b/0x5a7
================================================================

Fixes: ea5391e7b256 ("Bluetooth: hci_sync: Fix overwriting request callback")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
---
 net/bluetooth/hci_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 6ca4c0df9f9c..df3aa41e376d 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -4217,7 +4217,7 @@ static void hci_send_cmd_sync(struct hci_dev *hdev, struct sk_buff *skb)
 	if (hci_req_status_pend(hdev) &&
 	    !hci_dev_test_and_set_flag(hdev, HCI_CMD_PENDING)) {
 		kfree_skb(hdev->req_skb);
-		hdev->req_skb = skb_clone(skb, GFP_KERNEL);
+		hdev->req_skb = skb_clone(hdev->sent_cmd, GFP_KERNEL);
 	}
 
 	atomic_dec(&hdev->cmd_cnt);
-- 
2.44.0