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SubjectRe: [PATCH v3] bluetooth: hci_h5: fix memory leak in h5_close
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Hi,

On 10/4/20 7:17 AM, Anant Thazhemadam wrote:
> When h5_close() is called and !hu->serdev, h5 is directly freed.
> However, h5->rx_skb is not freed before h5 is freed, which causes
> a memory leak.
> Freeing h5->rx_skb (when !hu->serdev) fixes this memory leak before
> freeing h5.
>
> Fixes: ce945552fde4 ("Bluetooth: hci_h5: Add support for serdev enumerated devices")
> Reported-by: syzbot+6ce141c55b2f7aafd1c4@syzkaller.appspotmail.com
> Tested-by: syzbot+6ce141c55b2f7aafd1c4@syzkaller.appspotmail.com
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> ---
> Changes in v3:
> * Free h5->rx_skb when !hu->serdev, and fix the memory leak
> * Do not incorrectly and unnecessarily call serdev_device_close()
>
> Changes in v2:
> * Fixed the Fixes tag
>
> Hans de Goede also suggested calling h5_reset_rx() on close (for both, !hu->serdev
> and hu->serdev cases).
> However, doing so seems to lead to a null-ptr-dereference error,
> https://syzkaller.appspot.com/text?tag=CrashReport&x=136a9a5d900000,
> and for this reason, it has not been implemented.
>
> Instead, directly freeing h5->rx_skb seems to suffice in preventing the memory leak
> reported.
> And since h5 is freed immediately after freeing h5->rx_skb, assigning h5->rx_skb to
> be NULL isn't necessary.
>
> drivers/bluetooth/hci_h5.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/bluetooth/hci_h5.c b/drivers/bluetooth/hci_h5.c
> index e41854e0d79a..171e55c080ce 100644
> --- a/drivers/bluetooth/hci_h5.c
> +++ b/drivers/bluetooth/hci_h5.c
> @@ -248,8 +248,10 @@ static int h5_close(struct hci_uart *hu)
> if (h5->vnd && h5->vnd->close)
> h5->vnd->close(h5);
>
> - if (!hu->serdev)
> + if (!hu->serdev){
> + kfree_skb(h5->rx_skb);
> kfree(h5);
> + }
>
> return 0;
> }
>

To fully fix the memleak you also need to add a kfree_skb(h5->rx_skb);
call to the end of h5_serdev_remove(), because in the hu->serdev case
that is where the h5 struct will be free-ed (it is free-ed after that
function exits).

Regards,

Hans

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