From: Mauro Carvalho Chehab > Sent: 21 June 2021 14:40 > > As warned by smatch: > drivers/media/usb/uvc/uvc_v4l2.c:911 uvc_ioctl_g_input() error: doing dma on the stack (&i) > drivers/media/usb/uvc/uvc_v4l2.c:943 uvc_ioctl_s_input() error: doing dma on the stack (&i) > > those two functions call uvc_query_ctrl passing a pointer to > a data at the DMA stack. those are used to send URBs via > usb_control_msg(). Using DMA stack is not supported and should > not work anymore on modern Linux versions. > > So, use a kmalloc'ed buffer. ... > + buf = kmalloc(1, GFP_KERNEL); > + if (!buf) > + return -ENOMEM; > + > ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, chain->selector->id, > chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL, > - &i, 1); > + buf, 1); Thought... Is kmalloc(1, GFP_KERNEL) guaranteed to return a pointer into a cache line that will not be accessed by any other code? (This is slightly weaker than requiring a cache-line aligned pointer - but very similar.) Without that guarantee you can't use the returned buffer for read dma unless the memory accesses are coherent. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
