Hi Ivan, On Tue, Jul 15, 2025 at 8:38 PM Ivan Pravdin <ipravdin.official@xxxxxxxxx> wrote: > > 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.` > > As hdev->dump is used after dev_coredumpv, create temporary buffer to > hold hdev->dump data. > > Reported-by: syzbot+ac3c79181f6aecc5120c@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://lore.kernel.org/all/67eaa688.050a0220.1547ec.014a.GAE@xxxxxxxxxx It should probably close the syzkaller issue, which I assume is this one: https://syzkaller.appspot.com/bug?extid=ac3c79181f6aecc5120c > Fixes: b257e02ecc46 ("HCI: coredump: Log devcd dumps into the monitor") > Signed-off-by: Ivan Pravdin <ipravdin.official@xxxxxxxxx> > --- > 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); > + } > > > /* Send a copy to monitor as a diagnostic packet */ > skb = bt_skb_alloc(size, GFP_ATOMIC); > -- > 2.45.2 > What is wrong here the is code that attempt to send a copy to the monitor uses dump.head _after_ dev_coredumpv has freed it, so just changing the order shall make it work properly: diff --git a/net/bluetooth/coredump.c b/net/bluetooth/coredump.c index 819eacb38762..720cb79adf96 100644 --- a/net/bluetooth/coredump.c +++ b/net/bluetooth/coredump.c @@ -249,15 +249,15 @@ 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); - /* Send a copy to monitor as a diagnostic packet */ skb = bt_skb_alloc(size, GFP_ATOMIC); if (skb) { skb_put_data(skb, hdev->dump.head, size); hci_recv_diag(hdev, skb); } + + /* Emit a devcoredump with the available data */ + dev_coredumpv(&hdev->dev, hdev->dump.head, size, GFP_KERNEL); } static void hci_devcd_handle_pkt_complete(struct hci_dev *hdev -- Luiz Augusto von Dentz
