linux-kernel - Re: [PATCH v2] Bluetooth: coredump: Use tmp buffer with dev

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Message-ID: <r44coidqefd66owzl7fwgbtpjkfgwbayd7irzpbgcvifklwrjf@rimfqjmffdae>
Date: Wed, 16 Jul 2025 23:35:36 -0400
From: Ivan Pravdin <ipravdin.official@...il.com>
To: Paul Menzel <pmenzel@...gen.mpg.de>
Cc: marcel@...tmann.org, johan.hedberg@...il.com, luiz.dentz@...il.com, 
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzbot+ac3c79181f6aecc5120c@...kaller.appspotmail.com
Subject: Re: [PATCH v2] Bluetooth: coredump: Use tmp buffer with dev_coredumpv

On Wed, Jul 16, 2025 at 05:06:38AM GMT, Paul Menzel wrote:
> Dear Ivan,
> 
> 
> Thank you for your patch and fixing the report.
> 
> Am 16.07.25 um 02:37 schrieb Ivan Pravdin:
> 
> Personally, I’d start with the problem description.

I will add more details in v3.

> 
> > Create and use new vmalloc'ed buffer with dev_coredumpv. From
> > dev_coredumpv documentation:
> > 
> > `This function takes ownership of the vmalloc'ed data and will free
> > it when it is no longer used.`
> 
> You could use email/Markdown style citation by prepending the lines with `> `.

I will fix it in v3.

> 
> > As hdev->dump is used after dev_coredumpv, create temporary buffer to
> > hold hdev->dump data.
> > 
> > Reported-by: syzbot+ac3c79181f6aecc5120c@...kaller.appspotmail.com
> > Closes: https://lore.kernel.org/all/67eaa688.050a0220.1547ec.014a.GAE@google.com
> 
> Add a trace excerpt to the commit message?

I will add it in v3.

> 
> > Fixes: b257e02ecc46 ("HCI: coredump: Log devcd dumps into the monitor")
> > Signed-off-by: Ivan Pravdin <ipravdin.official@...il.com>
> > ---
> > v1 -> v2: Changed subject prefix to Bluetooth:
> > 
> >   net/bluetooth/coredump.c | 7 ++++++-
> >   1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/net/bluetooth/coredump.c b/net/bluetooth/coredump.c
> > index 819eacb38762..1232c9a94f95 100644
> > --- a/net/bluetooth/coredump.c
> > +++ b/net/bluetooth/coredump.c
> > @@ -243,6 +243,7 @@ static void hci_devcd_handle_pkt_pattern(struct hci_dev *hdev,
> >   static void hci_devcd_dump(struct hci_dev *hdev)
> >   {
> >   	struct sk_buff *skb;
> > +	char *coredump;
> >   	u32 size;
> >   	bt_dev_dbg(hdev, "state %d", hdev->dump.state);
> > @@ -250,7 +251,11 @@ static void hci_devcd_dump(struct hci_dev *hdev)
> >   	size = hdev->dump.tail - hdev->dump.head;
> >   	/* Emit a devcoredump with the available data */
> > -	dev_coredumpv(&hdev->dev, hdev->dump.head, size, GFP_KERNEL);
> > +	coredump = vmalloc(size);
> > +	if (coredump) {
> > +		memcpy(coredump, hdev->dump.head, size);
> > +		dev_coredumpv(&hdev->dev, coredump, size, GFP_KERNEL);
> > +	}
> 
> Should it be logged, if allocation fails?

Right, I will add it in v3.

> 
> >   	/* Send a copy to monitor as a diagnostic packet */
> >   	skb = bt_skb_alloc(size, GFP_ATOMIC);
> 
> 
> Kind regards,
> 
> Paul

	Ivan Pravdin