On Mon, Aug 01, 2011 at 11:04:11PM -0600, Adam Cozzette wrote: > On Mon, Aug 01, 2011 at 05:09:06PM -0400, Josh Boyer wrote: > > Hello, > > > > We have a report that the ums-realtek driver is generating a backtrace > > due to using stack variables for DMA buffers. The backtrace is below > > and you can view the bug report here: > > https://bugzilla.redhat.com/show_bug.cgi?id=720054 > > > > Looking through the code, it seems that every call to rts51x_read_mem, > > rts51x_write_mem, and rts51x_read_status passes a stack variable to > > rts51x_bulk_transport, which then calls usb_stor_bulk_transfer_buf with > > this and generates the backtrace. It is my understanding that the > > driver should be passing variables that are not on the stack and have > > been allocated with memory that will be suitable for the DMA api (e.g. > > kmalloc). > > > > Was this missed during the initial review and is anyone working on > > adapting the driver to be compliant? > > Could you try out this patch if it looks ok to you? I have not tested it because > unfortunately I don't have the hardware. Right now it generates some compile > warnings like this one: > > drivers/usb/storage/realtek_cr.c:419:40: warning: ‘buf[0]’ may be used uninitialized in this function [-Wuninitialized] > > It think they are harmless but I didn't see an obvious way to get rid of them, > so if you have any suggestions I would be glad to hear them. > > This patch changed rts51x_read_mem, rts51x_write_mem, and rts51x_read_status to > allocate temporary buffers with kmalloc. This way stack addresses are not used > for DMA when these functions call rts51x_bulk_transport. > > Signed-off-by: Adam Cozzette <acozzette@xxxxxxxxxx> This looks pretty good. I backported it to 3.0 and will do a scratch build for the bug reporter to test with. josh -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
