linux-kernel - [PATCH] xhci: Do not use GFP_KERNEL in (potentially) atomic context

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Date:   Fri, 14 Aug 2020 07:13:48 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     mathias.nyman@...el.com, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] xhci: Do not use GFP_KERNEL in (potentially) atomic context

'xhci_urb_enqueue()' is passed a 'mem_flags' argument, because "URBs may be
submitted in interrupt context" (see comment related to 'usb_submit_urb()'
in 'drivers/usb/core/urb.c')

So this flag should be used in all the calling chain.
Up to now, 'xhci_check_maxpacket()' which is only called from
'xhci_urb_enqueue()', uses GFP_KERNEL.

Be safe and pass the mem_flags to this function as well.

Fixes: ddba5cd0aeff ("xhci: Use command structures when queuing commands on the command ring")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
I'm not 100% sure of the Fixes tag. The commit is the only that introduced
this GFP_KERNEL, but I've not checked what was the behavior before that.

If the patch is correct, I guess that a cc stable should be welcome.
---
 drivers/usb/host/xhci.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 3c41b14ecce7..b536f18e4cfd 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1382,7 +1382,7 @@ static int xhci_configure_endpoint(struct xhci_hcd *xhci,
  * we need to issue an evaluate context command and wait on it.
  */
 static int xhci_check_maxpacket(struct xhci_hcd *xhci, unsigned int slot_id,
-		unsigned int ep_index, struct urb *urb)
+		unsigned int ep_index, struct urb *urb, gfp_t mem_flags)
 {
 	struct xhci_container_ctx *out_ctx;
 	struct xhci_input_control_ctx *ctrl_ctx;
@@ -1413,7 +1413,7 @@ static int xhci_check_maxpacket(struct xhci_hcd *xhci, unsigned int slot_id,
 		 * changes max packet sizes.
 		 */
 
-		command = xhci_alloc_command(xhci, true, GFP_KERNEL);
+		command = xhci_alloc_command(xhci, true, mem_flags);
 		if (!command)
 			return -ENOMEM;
 
@@ -1509,7 +1509,7 @@ static int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 		 */
 		if (urb->dev->speed == USB_SPEED_FULL) {
 			ret = xhci_check_maxpacket(xhci, slot_id,
-					ep_index, urb);
+					ep_index, urb, mem_flags);
 			if (ret < 0) {
 				xhci_urb_free_priv(urb_priv);
 				urb->hcpriv = NULL;
-- 
2.25.1