From: Jia-Ju Bai baijiaju@buaa.edu.cn

stable inclusion from stable-v4.19.299 commit fed492aa6493a91a77ebd51da6fb939c98d94a0d category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9RFRD CVE: CVE-2023-52855

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ 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@buaa.edu.cn Link: https://lore.kernel.org/r/20230926024404.832096-1-baijiaju@buaa.edu.cn Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: dinglongwei dinglongwei1@huawei.com --- drivers/usb/dwc2/hcd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c index 2fe0b953921f..8b8c113b7267 100644 --- a/drivers/usb/dwc2/hcd.c +++ b/drivers/usb/dwc2/hcd.c @@ -4844,8 +4844,8 @@ 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: