This is a note to let you know that I've just added the patch titled
usb: dwc2: fix possible NULL pointer dereference caused by driver concurrency
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-dwc2-fix-possible-null-pointer-dereference-cause.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d77d180072f1f518e4e1bacd66f7fbec30e9100f
Author: Jia-Ju Bai <baijiaju@xxxxxxxxxxx>
Date: Tue Sep 26 10:44:04 2023 +0800
usb: dwc2: fix possible NULL pointer dereference caused by driver concurrency
[ Upstream commit ef307bc6ef04e8c1ea843231db58e3afaafa9fa6 ]
In _dwc2_hcd_urb_enqueue(), "urb->hcpriv = NULL" is executed without
holding the lock "hsotg->lock". In _dwc2_hcd_urb_dequeue():
spin_lock_irqsave(&hsotg->lock, flags);
...
if (!urb->hcpriv) {
dev_dbg(hsotg->dev, "## urb->hcpriv is NULL ##\n");
goto out;
}
rc = dwc2_hcd_urb_dequeue(hsotg, urb->hcpriv); // Use urb->hcpriv
...
out:
spin_unlock_irqrestore(&hsotg->lock, flags);
When _dwc2_hcd_urb_enqueue() and _dwc2_hcd_urb_dequeue() are
concurrently executed, the NULL check of "urb->hcpriv" can be executed
before "urb->hcpriv = NULL". After urb->hcpriv is NULL, it can be used
in the function call to dwc2_hcd_urb_dequeue(), which can cause a NULL
pointer dereference.
This possible bug is found by an experimental static analysis tool
developed by myself. This tool analyzes the locking APIs to extract
function pairs that can be concurrently executed, and then analyzes the
instructions in the paired functions to identify possible concurrency
bugs including data races and atomicity violations. The above possible
bug is reported, when my tool analyzes the source code of Linux 6.5.
To fix this possible bug, "urb->hcpriv = NULL" should be executed with
holding the lock "hsotg->lock". After using this patch, my tool never
reports the possible bug, with the kernelconfiguration allyesconfig for
x86_64. Because I have no associated hardware, I cannot test the patch
in runtime testing, and just verify it according to the code logic.
Fixes: 33ad261aa62b ("usb: dwc2: host: spinlock urb_enqueue")
Signed-off-by: Jia-Ju Bai <baijiaju@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230926024404.832096-1-baijiaju@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index cfda883185838..91fa831328fce 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -4845,8 +4845,8 @@ static int _dwc2_hcd_urb_enqueue(struct usb_hcd *hcd, struct urb *urb,
if (qh_allocated && qh->channel && qh->channel->qh == qh)
qh->channel->qh = NULL;
fail2:
- spin_unlock_irqrestore(&hsotg->lock, flags);
urb->hcpriv = NULL;
+ spin_unlock_irqrestore(&hsotg->lock, flags);
kfree(qtd);
qtd = NULL;
fail1:
