linux-kernel - Re: [PATCH] Bluetooth: purge unhandled skbs

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Message-ID: <s5hr3e8i70r.wl-tiwai@suse.de>
Date:	Thu, 14 Apr 2016 16:45:08 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	Jiri Slaby <jslaby@...e.cz>,
	Johan Hedberg <johan.hedberg@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Gustavo F. Padovan" <gustavo@...ovan.org>,
	linux-bluetooth@...r.kernel.org,
	"stable 3 . 13+" <stable@...r.kernel.org>
Subject: Re: [PATCH] Bluetooth: purge unhandled skbs

On Thu, 14 Apr 2016 16:41:34 +0200,
Marcel Holtmann wrote:
> 
> Hi Takashi,
> 
> >>> The write handler allocates skbs and queues them into data->readq.
> >>> Read side should read them, if there is any. If there is none, skbs
> >>> should be dropped by hdev->flush. But this happens only if the device
> >>> is HCI_UP, i.e. hdev->power_on work was triggered already. When it was
> >>> not, skbs stay allocated in the queue when /dev/vhci is closed. So
> >>> purge the queue in ->release.
> >>> 
> >>> Program to reproduce:
> >>> 	#include <err.h>
> >>> 	#include <fcntl.h>
> >>> 	#include <stdio.h>
> >>> 	#include <unistd.h>
> >>> 
> >>> 	#include <sys/stat.h>
> >>> 	#include <sys/types.h>
> >>> 	#include <sys/uio.h>
> >>> 
> >>> 	int main()
> >>> 	{
> >>> 		char buf[] = { 0xff, 0 };
> >>> 		struct iovec iov = {
> >>> 			.iov_base = buf,
> >>> 			.iov_len = sizeof(buf),
> >>> 		};
> >>> 		int fd;
> >>> 
> >>> 		while (1) {
> >>> 			fd = open("/dev/vhci", O_RDWR);
> >>> 			if (fd < 0)
> >>> 				err(1, "open");
> >>> 
> >>> 			usleep(50);
> >>> 
> >>> 			if (writev(fd, &iov, 1) < 0)
> >>> 				err(1, "writev");
> >>> 
> >>> 			usleep(50);
> >>> 
> >>> 			close(fd);
> >>> 		}
> >>> 
> >>> 		return 0;
> >>> 	}
> >>> 
> >>> Result:
> >>> kmemleak: 4609 new suspected memory leaks
> >>> unreferenced object 0xffff88059f4d5440 (size 232):
> >>> comm "vhci", pid 1084, jiffies 4294912542 (age 37569.296s)
> >>> hex dump (first 32 bytes):
> >>>   20 f0 23 87 05 88 ff ff 20 f0 23 87 05 88 ff ff   .#..... .#.....
> >>>   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >>> backtrace:
> >>> ...
> >>>   [<ffffffff81ece010>] __alloc_skb+0x0/0x5a0
> >>>   [<ffffffffa021886c>] vhci_create_device+0x5c/0x580 [hci_vhci]
> >>>   [<ffffffffa0219436>] vhci_write+0x306/0x4c8 [hci_vhci]
> >>> 
> >>> Fixes: 23424c0d31 (Bluetooth: Add support creating virtual AMP controllers)
> >>> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> >>> Cc: Marcel Holtmann <marcel@...tmann.org>
> >>> Cc: Gustavo Padovan <gustavo@...ovan.org>
> >>> Cc: Johan Hedberg <johan.hedberg@...il.com>
> >>> Cc: <linux-bluetooth@...r.kernel.org>
> >>> Cc: stable 3.13+ <stable@...r.kernel.org>
> >>> ---
> >>> drivers/bluetooth/hci_vhci.c | 1 +
> >>> 1 file changed, 1 insertion(+)
> >> 
> >> patch has been applied to bluetooth-next tree.
> > 
> > Could you check another race of vhci mentioned in the thread?
> >  https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1106134.html
> > 
> > If the suggested fix is OK, I'll submit a properly cooked patch.
> 
> lets get the patch send to the mailing list and then I can have a look at it. I might need to test the final patch so that it works with legacy userspace.

Alright, will submit it soon later.


thanks,

Takashi