linux-kernel - [ 037/175] USB: ums_realtek: do not use stack memory for DMA in __do_config

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Date:	Fri, 30 Mar 2012 12:49:02 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Josh Boyer <jwboyer@...hat.com>
Subject: [ 037/175] USB: ums_realtek: do not use stack memory for DMA in __do_config_autodelink

3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Josh Boyer <jwboyer@...hat.com>

commit 4898e07174b79013afd2b422ef6c4336ef8e6783 upstream.

__do_config_autodelink passes the data variable to the transport function.
If the calling functions pass a stack variable, this will eventually trigger
a DMA-API debug backtrace for mapping stack memory in the DMA buffer.  Fix
this by calling kmemdup for the passed data instead.

Signed-off-by: Josh Boyer <jwboyer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/storage/realtek_cr.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/usb/storage/realtek_cr.c
+++ b/drivers/usb/storage/realtek_cr.c
@@ -507,9 +507,14 @@ static int __do_config_autodelink(struct
 {
 	int retval;
 	u8 cmnd[12] = {0};
+	u8 *buf;
 
 	US_DEBUGP("%s, addr = 0xfe47, len = %d\n", __FUNCTION__, len);
 
+	buf = kmemdup(data, len, GFP_NOIO);
+	if (!buf)
+		return USB_STOR_TRANSPORT_ERROR;
+
 	cmnd[0] = 0xF0;
 	cmnd[1] = 0x0E;
 	cmnd[2] = 0xfe;
@@ -517,7 +522,8 @@ static int __do_config_autodelink(struct
 	cmnd[4] = (u8)(len >> 8);
 	cmnd[5] = (u8)len;
 
-	retval = rts51x_bulk_transport_special(us, 0, cmnd, 12, data, len, DMA_TO_DEVICE, NULL);
+	retval = rts51x_bulk_transport_special(us, 0, cmnd, 12, buf, len, DMA_TO_DEVICE, NULL);
+	kfree(buf);
 	if (retval != USB_STOR_TRANSPORT_GOOD) {
 		return -EIO;
 	}


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