From: Ian Abbott <abbotti@mev.co.uk>
To: devel@driverdev.osuosl.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ian Abbott <abbotti@mev.co.uk>,
H Hartley Sweeten <hsweeten@visionengravers.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/2] staging: comedi: vmk80xx: Fix possible double-free of ->usb_rx_buf
Date: Mon, 15 Apr 2019 12:52:30 +0100 [thread overview]
Message-ID: <20190415115230.7288-1-abbotti@mev.co.uk> (raw)
In-Reply-To: <20190415111015.8257-3-abbotti@mev.co.uk>
`vmk80xx_alloc_usb_buffers()` is called from `vmk80xx_auto_attach()` to
allocate RX and TX buffers for USB transfers. It allocates
`devpriv->usb_rx_buf` followed by `devpriv->usb_tx_buf`. If the
allocation of `devpriv->usb_tx_buf` fails, it frees
`devpriv->usb_rx_buf`, leaving the pointer set dangling, and returns an
error. Later, `vmk80xx_detach()` will be called from the core comedi
module code to clean up. `vmk80xx_detach()` also frees both
`devpriv->usb_rx_buf` and `devpriv->usb_tx_buf`, but
`devpriv->usb_rx_buf` may have already been freed, leading to a
double-free error. Fix it by removing the call to
`kfree(devpriv->usb_rx_buf)` from `vmk80xx_alloc_usb_buffers()`, relying
on `vmk80xx_detach()` to free the memory.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
---
v2: Fix commit message because it incorrectly indicated that the call to
`kfree()` was being removed from `vmk80xx_auto_attach()`, not
`vmk80xx_alloc_usb_buffers().
---
drivers/staging/comedi/drivers/vmk80xx.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/staging/comedi/drivers/vmk80xx.c b/drivers/staging/comedi/drivers/vmk80xx.c
index b035d662390b..65dc6c51037e 100644
--- a/drivers/staging/comedi/drivers/vmk80xx.c
+++ b/drivers/staging/comedi/drivers/vmk80xx.c
@@ -682,10 +682,8 @@ static int vmk80xx_alloc_usb_buffers(struct comedi_device *dev)
size = usb_endpoint_maxp(devpriv->ep_tx);
devpriv->usb_tx_buf = kzalloc(size, GFP_KERNEL);
- if (!devpriv->usb_tx_buf) {
- kfree(devpriv->usb_rx_buf);
+ if (!devpriv->usb_tx_buf)
return -ENOMEM;
- }
return 0;
}
--
2.20.1
prev parent reply other threads:[~2019-04-15 11:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-15 11:10 [PATCH 0/2] staging: comedi: vmk80xx: Fix a couple of bugs Ian Abbott
2019-04-15 11:10 ` [PATCH 1/2] staging: comedi: vmk80xx: Fix use of uninitialized semaphore Ian Abbott
2019-04-15 11:10 ` [PATCH 2/2] staging: comedi: vmk80xx: Fix possible double-free of ->usb_rx_buf Ian Abbott
2019-04-15 11:52 ` Ian Abbott [this message]
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