On Tue, Apr 14, 2020 at 5:50 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, 14 Apr 2020, Andrey Konovalov wrote: > > > On Wed, Mar 25, 2020 at 5:14 PM <glider@xxxxxxxxxx> wrote: > > > > > > Depending on the value of is_out kmsan_handle_urb() KMSAN either > > > marks the data copied to the kernel from a USB device as initialized, > > > or checks the data sent to the device for being initialized. > > > > > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > > > To: Alexander Potapenko <glider@xxxxxxxxxx> > > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > > Cc: Eric Dumazet <edumazet@xxxxxxxxxx> > > > Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx> > > > Cc: Petr Mladek <pmladek@xxxxxxxx> > > > Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx> > > > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > > Cc: Marco Elver <elver@xxxxxxxxxx> > > > Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > > > Cc: linux-mm@xxxxxxxxx > > > > > > --- > > > > > > This patch was previously called "kmsan: call KMSAN hooks where needed" > > > > > > v4: > > > - split this patch away > > > > > > Change-Id: Idd0f8ce858975112285706ffb7286f570bd3007b > > > --- > > > drivers/usb/core/urb.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c > > > index da923ec176122..4a0b0ac0f52f9 100644 > > > --- a/drivers/usb/core/urb.c > > > +++ b/drivers/usb/core/urb.c > > > @@ -8,6 +8,7 @@ > > > #include <linux/bitops.h> > > > #include <linux/slab.h> > > > #include <linux/log2.h> > > > +#include <linux/kmsan-checks.h> > > > #include <linux/usb.h> > > > #include <linux/wait.h> > > > #include <linux/usb/hcd.h> > > > @@ -402,6 +403,7 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags) > > > URB_SETUP_MAP_SINGLE | URB_SETUP_MAP_LOCAL | > > > URB_DMA_SG_COMBINED); > > > urb->transfer_flags |= (is_out ? URB_DIR_OUT : URB_DIR_IN); > > > + kmsan_handle_urb(urb, is_out); > > > > I guess this could simply accept urb and then check > > urb->transfer_flags instead of also accepting is_out? > > > > Alan, do you think this is a good place for a call to > > kmsan_handle_urb(), which is supposed to check that the memory we pass > > to a USB device is initialized (so we don't leak uninitialized memory) > > and mark memory received from the device as initialized? You can find > > the implementation here: > > > > https://github.com/google/kmsan/commit/491a67cf03fa9e0f240fd6eb53a6074e4bfd1a2c#diff-020c941e2b8fc67f5ddca598cd954d57R322 > > This has got a couple of problems. > > Firstly, for control URBs it doesn't check urb->setup_packet, which > should always be initialized regardless of the direction because it > always gets sent to the device. Ah, yes, we actually had an info-leak report for a bug in the sound subsystem that was leaking data this way, which was misattributed to raw-gadget. This makes sense to add and seems quite easy. > Secondly, some URBs use scatter-gather transfers, and they don't always > store the buffer address in urb->transfer_buffer (indeed, sometimes the > buffer is located outside of the kernel's address map). Instead they > use urb->sg and urb->num_sgs. To get an idea for how it all works, > look at usb_hcd_map_urb_for_dma() in hcd.c. Oh, this is something we need to look into. > Thirdly, the information we get back from the device doesn't always > cover the entire transfer buffer; sometimes the device sends less data > than we asked for. Perhaps you don't care very much about this case. So you mean that we should look at actual_length rather than transfer_buffer_length when initializing memory that comes from the device? Thank you, Alan!
