The function 'ep0_rx_state()' accessed 'mreq->request' before verifying that mreq was valid. If 'next_ep0_request()' returned NULL, this could lead to a NULL pointer dereference. The return value of 'next_ep0_request()' is checked in every other code path except here. It appears that the intended 'if (mreq)' check was mistakenly written as 'if (req)', since the req pointer cannot be NULL when mreq is not NULL.

Initialize 'mreq' and 'req' to NULL by default, and switch 'req' NULL-checking to 'mreq' non-NULL check to prevent invalid memory access.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: df2069acb005 ("usb: Add MediaTek USB3 DRD driver") Signed-off-by: Pavel Zhigulin Pavel.Zhigulin@kaspersky.com --- v2: Add stable@vger.kernel.org to CC list v1: https://lore.kernel.org/all/20251027193152.3906497-1-Pavel.Zhigulin@kaspersk...

drivers/usb/mtu3/mtu3_gadget_ep0.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/mtu3/mtu3_gadget_ep0.c b/drivers/usb/mtu3/mtu3_gadget_ep0.c index e4fd1bb14a55..ee7466ca4d99 100644 --- a/drivers/usb/mtu3/mtu3_gadget_ep0.c +++ b/drivers/usb/mtu3/mtu3_gadget_ep0.c @@ -508,8 +508,8 @@ static int handle_standard_request(struct mtu3 *mtu, /* receive an data packet (OUT) */ static void ep0_rx_state(struct mtu3 *mtu) { - struct mtu3_request *mreq; - struct usb_request *req; + struct mtu3_request *mreq = NULL; + struct usb_request *req = NULL; void __iomem *mbase = mtu->mac_base; u32 maxp; u32 csr; @@ -519,10 +519,11 @@ static void ep0_rx_state(struct mtu3 *mtu)

csr = mtu3_readl(mbase, U3D_EP0CSR) & EP0_W1C_BITS; mreq = next_ep0_request(mtu); - req = &mreq->request;

/* read packet and ack; or stall because of gadget driver bug */ - if (req) { + if (mreq) { + req = &mreq->request; + void *buf = req->buf + req->actual; unsigned int len = req->length - req->actual;

-- 2.43.0