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authorPete Zaitcev <zaitcev@redhat.com>2009-06-11 08:53:20 -0600
committerGreg Kroah-Hartman <gregkh@suse.de>2009-09-23 06:46:19 -0700
commit4e9e92003529e5c7bb11281f7c2c9b3fe8858403 (patch)
tree07169c9a996a119aebb5865a76ff1177afe90a22 /drivers/usb/mon/mon_text.c
parentf4e2332cfcf900e0a926c4e0fc35f751bcbcaa1b (diff)
USB: usbmon: end ugly tricks with DMA peeking
This patch fixes crashes when usbmon attempts to access GART aperture. The old code attempted to take a bus address and convert it into a virtual address, which clearly was impossible on systems with actual IOMMUs. Let us not persist in this foolishness, and use transfer_buffer in all cases instead. I think downsides are negligible. The ones I see are: - A driver may pass an address of one buffer down as transfer_buffer, and entirely different entity mapped for DMA, resulting in misleading output of usbmon. Note, however, that PIO based controllers would do transfer the same data that usbmon sees here. - Out of tree drivers may crash usbmon if they store garbage in transfer_buffer. I inspected the in-tree drivers, and clarified the documentation in comments. - Drivers that use get_user_pages will not be possible to monitor. I only found one driver with this problem (drivers/staging/rspiusb). - Same happens with with usb_storage transferring from highmem, but it works fine on 64-bit systems, so I think it's not a concern. At least we don't crash anymore. Why didn't we do this in 2.6.10? That's because back in those days it was popular not to fill in transfer_buffer, so almost all traffic would be invisible (e.g. all of HID was like that). But now, the tree is almost 100% PIO friendly, so we can do the right thing at last. Signed-off-by: Pete Zaitcev <zaitcev@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/mon/mon_text.c')
-rw-r--r--drivers/usb/mon/mon_text.c14
1 files changed, 0 insertions, 14 deletions
diff --git a/drivers/usb/mon/mon_text.c b/drivers/usb/mon/mon_text.c
index a7eb4c99342..9f1a9227ebe 100644
--- a/drivers/usb/mon/mon_text.c
+++ b/drivers/usb/mon/mon_text.c
@@ -150,20 +150,6 @@ static inline char mon_text_get_data(struct mon_event_text *ep, struct urb *urb,
return '>';
}
- /*
- * The check to see if it's safe to poke at data has an enormous
- * number of corner cases, but it seems that the following is
- * more or less safe.
- *
- * We do not even try to look at transfer_buffer, because it can
- * contain non-NULL garbage in case the upper level promised to
- * set DMA for the HCD.
- */
- if (urb->dev->bus->uses_dma &&
- (urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)) {
- return mon_dmapeek(ep->data, urb->transfer_dma, len);
- }
-
if (urb->transfer_buffer == NULL)
return 'Z'; /* '0' would be not as pretty. */