diff options
| author | Andrey Konovalov <andreyknvl@google.com> | 2020-10-16 15:57:45 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-10-28 13:10:54 +0100 |
| commit | aee9ddb1d3718d3ba05b50c51622d7792ae749c9 (patch) | |
| tree | dbfc82c0703ddbb03c628f0246746ff8c0b6dc0e /drivers/usb/core/hcd.c | |
| parent | ecbb4dac5f6ccbc5443609ec72021994b662e06d (diff) | |
kcov, usb: only collect coverage from __usb_hcd_giveback_urb in softirq
Currently there's a KCOV remote coverage collection section in
__usb_hcd_giveback_urb(). Initially that section was added based on the
assumption that usb_hcd_giveback_urb() can only be called in interrupt
context as indicated by a comment before it. This is what happens when
syzkaller is fuzzing the USB stack via the dummy_hcd driver.
As it turns out, it's actually valid to call usb_hcd_giveback_urb() in task
context, provided that the caller turned off the interrupts; USB/IP does
exactly that. This can lead to a nested KCOV remote coverage collection
sections both trying to collect coverage in task context. This isn't
supported by KCOV, and leads to a WARNING.
Change __usb_hcd_giveback_urb() to only call kcov_remote_*() callbacks
when it's being executed in a softirq. As the result, the coverage from
USB/IP related usb_hcd_giveback_urb() calls won't be collected, but the
WARNING is fixed.
A potential future improvement would be to support nested remote coverage
collection sections, but this patch doesn't address that.
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://lore.kernel.org/r/f3a7a153f0719cb53ec385b16e912798bd3e4cf9.1602856358.git.andreyknvl@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/core/hcd.c')
| -rw-r--r-- | drivers/usb/core/hcd.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index 90ce5841d9f5..60886a7464c3 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -1647,9 +1647,16 @@ static void __usb_hcd_giveback_urb(struct urb *urb) /* pass ownership to the completion handler */ urb->status = status; - kcov_remote_start_usb((u64)urb->dev->bus->busnum); + /* + * This function can be called in task context inside another remote + * coverage collection section, but KCOV doesn't support that kind of + * recursion yet. Only collect coverage in softirq context for now. + */ + if (in_serving_softirq()) + kcov_remote_start_usb((u64)urb->dev->bus->busnum); urb->complete(urb); - kcov_remote_stop(); + if (in_serving_softirq()) + kcov_remote_stop(); usb_anchor_resume_wakeups(anchor); atomic_dec(&urb->use_count); |