In the current implementation, the check_event_buf call reads the GEVNTCOUNT register to determine the amount of event data generated and copies it from ev->buf to ev->cache after masking interrupt. During copy if the amount of data to be copied is more than (length - lpos), we fill the ev->cache till the end of 4096 byte buffer allocated and then start filling from the top (lpos = 0). In one instance of SMMU crash it is observed that GEVNTCOUNT register reads more than 4096 bytes: dwc3_readl base=0xffffffc0091dc000 offset=50188 value=63488 (offset = 50188 -> 0xC40C) -> reads 63488 bytes As per crash dump: dwc->lpos = 2056 and evt->buf is at 0xFFFFFFC009185000 and the crash is at 0xFFFFFFC009186000. The diff which is exactly 0x1000 bytes. We first memcpy 2040 bytes from (buf + lpos) to (buf + 0x1000). And then we copy the rest of the data (64388 - 2040) from beginning of dwc->ev_buf. While doing so we go beyond bounds as we are trying to memcpy 62348 bytes into a 4K buffer resulting in crash. Fix this by ignoring the interrupt when GEVNTCOUNT register reads a value more than the event ring allocated. Signed-off-by: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx> --- Changes in v2: Instead of fixing amount of data being copied from ring, ignored the interrupt when count is corrupt as per suggestion from Thinh. Link to v1: https://lore.kernel.org/all/20230521100330.22478-1-quic_kriskura@xxxxxxxxxxx/ drivers/usb/dwc3/gadget.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 858fe4c299b7..e27933fdcce3 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -4451,6 +4451,7 @@ static irqreturn_t dwc3_thread_interrupt(int irq, void *_evt) static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt) { struct dwc3 *dwc = evt->dwc; + int ret = IRQ_WAKE_THREAD; u32 amount; u32 count; @@ -4480,6 +4481,12 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt) if (!count) return IRQ_NONE; + if (count > evt->length) { + dev_err(dwc->dev, "GEVTCOUNT corrupt\n"); + ret = IRQ_NONE; + goto done; + } + evt->count = count; evt->flags |= DWC3_EVENT_PENDING; @@ -4493,9 +4500,10 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt) if (amount < count) memcpy(evt->cache, evt->buf, count - amount); +done: dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count); - return IRQ_WAKE_THREAD; + return ret; } static irqreturn_t dwc3_interrupt(int irq, void *_evt) -- 2.42.0
